Pilot sequence transmission method and apparatus

ABSTRACT

The present invention discloses a pilot sequence transmission method and apparatus. A terminal device determines a first pilot number, determines a first pilot sequence and a second pilot sequence according to the first pilot number, respectively maps the first pilot sequence and the second pilot sequence to a first OFDM symbol and a second OFDM symbol of a grant free transmission resource, and sends the first pilot sequence and the second pilot sequence by using the first OFDM symbol and the second OFDM symbol. Therefore, a network device can determine activeness of the terminal device by detecting the first pilot sequence, and can detect only the second pilot sequence corresponding to the first pilot sequence, and does not need to detect all possible second pilot sequences, so that a quantity of detected pilots can be significantly reduced, and pilot detection complexity is reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2015/082851, filed on Jun. 30, 2015, which is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

The present invention relates to the communications field, and inparticular, to a pilot sequence transmission method and apparatus in thecommunications field.

BACKGROUND

A current communications system mainly supports voice communication anddata communication. Usually, a quantity of connections supported by aconventional base station is limited, and is easy to be implemented.However, a next-generation mobile communications system not only needsto support conventional voice communication and data communication, butalso supports machine to machine (M2M) communication that is alsoreferred to as machine type communication (MTC). According toprediction, by 2020, a quantity of MTC devices connected to networks mayreach 50 to 100 billion, and this may far exceed a current quantity ofconnections.

For an MTC type service, because service types of the MTC type servicediffer from each other, network requirements differ greatly. Generally,there may be two services having the following requirements: One is aservice that requires reliable transmission but is not sensitive to adelay, and the other is a service that requires a low delay andhigh-reliability transmission. It is relatively easy to process theservice that requires reliable transmission but is not sensitive to adelay. However, for the service that requires a low delay andhigh-reliability transmission, if transmission is unreliable,retransmission is caused and an excessively large transmission delay iscaused, and consequently, the requirements cannot be satisfied.

To handle a large quantity of MTC type services in a future network andsatisfy low-delay and high-reliability service transmission, an uplinkgrant free transmission solution is proposed. In a grant freetransmission system, there are a large quantity of terminal devices, butthere are also an extremely small quantity of terminal devices thataccess a network, and the terminal device may randomly select a grantfree transmission resource to send data. Currently, a network deviceneeds to detect each pilot, to determine an active terminal device.

Currently, in a Long Term Evolution (LTE) system, an uplink pilotsequence includes a demodulation reference signal (DMRS) and a soundingreference signal (SRS). The DMRS is used for channel estimation, so thatuplink data is demodulated according to a channel estimation result, andthe SRS is used for uplink channel quality measurement and occupies anentire frequency band.

If the DMRS in the LTE system is used in an uplink grant freetransmission system, the network device needs to detect every possibleDMRS. A common DMRS detection method is: converting a received frequencydomain signal to a time domain, to perform windowing and noise reductionprocessing. In this conversion process, inverse fast Fourier transform(IFFT) and fast Fourier transform (FFT) operations are required, andcomplexity is extremely high.

Therefore, to reduce pilot detection complexity becomes a technicalproblem urgently to be resolved in the grant free transmission system.

SUMMARY

In view of this, embodiments of the present invention provide a pilotsequence transmission method and apparatus, to resolve a problem of highpilot detection complexity.

According to a first aspect, a pilot sequence transmission method isprovided, where the method includes: determining a first pilot sequenceused to indicate whether a terminal device is in an active state;determining a second pilot sequence used for uplink data demodulation;mapping the first pilot sequence to a first orthogonal frequencydivision multiplexing OFDM symbol of a grant free transmission resource;mapping the second pilot sequence to a second OFDM symbol of the grantfree transmission resource; and sending the first pilot sequence and thesecond pilot sequence by using the first OFDM symbol and the second OFDMsymbol.

With reference to the first aspect, in a first possible implementationof the first aspect, the method further includes: determining a firstpilot number; the determining a first pilot sequence used to indicatewhether a terminal device is in an active state includes: determiningthe first pilot sequence according to the first pilot number; and thedetermining a second pilot sequence used for uplink data demodulationincludes: determining the second pilot sequence according to the firstpilot number.

With reference to the first possible implementation of the first aspect,in a second possible implementation of the first aspect, the determininga first pilot number includes: determining the first pilot numberaccording to an identifier of the terminal device; or determining thefirst pilot number according to an identifier of the grant freetransmission resource and an identifier of the terminal device; orgenerating the first pilot number by using a random number generator.

With reference to the first aspect, or the first or the second possibleimplementation of the first aspect, in a third possible implementationof the first aspect, the mapping the first pilot sequence to a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource includes: mapping the first pilot sequence to apart of a subband of the first OFDM symbol of the grant freetransmission resource.

With reference to the third possible implementation of the first aspect,in a fourth possible implementation of the first aspect, an element ofthe first pilot sequence is a non-zero element.

With reference to the third possible implementation of the first aspect,in a fifth possible implementation of the first aspect, the first pilotsequence includes a first pilot sub-sequence and a second pilotsub-sequence, each element of the first pilot sub-sequence is a zeroelement, and an element of the second pilot sub-sequence is a non-zeroelement.

With reference to any one of the third to the fifth possibleimplementations of the first aspect, in a sixth possible implementationof the first aspect, the mapping the first pilot sequence to a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource includes: mapping the non-zero element included inthe first pilot sequence to a first subband of the first OFDM symbol ofthe grant free transmission resource, where the first subband includes Mresource elements REs, a non-zero symbol formed after the non-zeroelement is mapped is an M-order Walsh code, and M is a positive integerand is an exponential power of 2.

With reference to the sixth possible implementation of the first aspect,in a seventh possible implementation of the first aspect, the REsincluded in the first subband are M consecutive REs.

With reference to any one of the first aspect or the first to theseventh possible implementations of the first aspect, in an eighthpossible implementation of the first aspect, the mapping the first pilotsequence to a first orthogonal frequency division multiplexing OFDMsymbol of a grant free transmission resource includes: repeatedlymapping the first pilot sequence to different first OFDM symbols of thegrant free transmission resource or different subbands of the first OFDMsymbol of the grant free transmission resource.

With reference to any one of the first aspect or the first to the eighthpossible implementations of the first aspect, in a ninth possibleimplementation of the first aspect, the first pilot sequence is inone-to-one correspondence with the second pilot sequence.

With reference to the ninth possible implementation of the first aspect,in a tenth possible implementation of the first aspect, the second pilotsequence is a sub-sequence combination including multiple sub-sequences.

With reference to the tenth possible implementation of the first aspect,in an eleventh possible implementation of the first aspect, the mappingthe second pilot sequence to a second OFDM symbol of the grant freetransmission resource includes: mapping at least two of the multiplesub-sequences included in the second pilot sequence to a same secondOFDM symbol of the grant free transmission resource.

With reference to the eleventh possible implementation of the firstaspect, in a twelfth possible implementation of the first aspect, themapping the second pilot sequence to a second OFDM symbol of the grantfree transmission resource includes: mapping all the multiplesub-sequences included in the second pilot sequence to a same secondOFDM symbol of the grant free transmission resource.

With reference to the eleventh possible implementation of the firstaspect, in a thirteenth possible implementation of the first aspect, themapping the second pilot sequence to a second OFDM symbol of the grantfree transmission resource includes: separately mapping at least two ofthe multiple sub-sequences included in the second pilot sequence todifferent subbands of a same second OFDM symbol of the grant freetransmission resource.

With reference to the tenth possible implementation of the first aspect,in a fourteenth possible implementation of the first aspect, the mappingthe second pilot sequence to a second OFDM symbol of the grant freetransmission resource includes: separately mapping all the multiplesub-sequences included in the second pilot sequence to different secondOFDM symbols of the grant free transmission resource.

With reference to the fourteenth possible implementation of the firstaspect, in a fifteenth possible implementation of the first aspect, themapping the second pilot sequence to a second OFDM symbol of the grantfree transmission resource includes: separately mapping all the multiplesub-sequences included in the second pilot sequence to entire frequencybands of the different second OFDM symbols of the grant freetransmission resource, where the second OFDM symbols are different fromthe first OFDM symbol.

With reference to any one of the tenth to the fifteenth possibleimplementations of the first aspect, in a sixteenth possibleimplementation of the first aspect, the second pilot sequence isgenerated by using multiple cyclic shift values, and the multiple cyclicshift values are in one-to-one correspondence with the multiplesub-sequences.

With reference to any one of the first aspect or the first to thesixteenth possible implementations of the first aspect, in a seventeenthpossible implementation of the first aspect, the mapping the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes: repeatedly mapping the second pilot sequence todifferent second OFDM symbols of the grant free transmission resource.

With reference to any one of the first aspect or the first to theseventeenth possible implementations of the first aspect, in aneighteenth possible implementation of the first aspect, the determininga first pilot sequence used to indicate whether a terminal device is inan active state includes: selecting the first pilot sequence from afirst pilot sequence set.

With reference to any one of the first aspect or the first to theeighteenth possible implementations of the first aspect, in a nineteenthpossible implementation of the first aspect, the determining a secondpilot sequence used for uplink data demodulation includes:

selecting the second pilot sequence from a second pilot sequence set.

With reference to any one of the first aspect or the first to thenineteenth possible implementations of the first aspect, in a twentiethpossible implementation of the first aspect, the grant free transmissionresource is a transmission resource combining time and frequency, or atransmission resource combining time, frequency, and code domains.

With reference to any one of the first aspect or the first to thetwentieth possible implementations of the first aspect, in atwenty-first possible implementation of the first aspect, the method isapplied to device-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

According to a second aspect, a pilot sequence transmission method isprovided, where the method includes: detecting, on a first orthogonalfrequency division multiplexing OFDM symbol of a grant free transmissionresource, a first pilot sequence sent by a terminal device, where thefirst pilot sequence is used to indicate whether the terminal device isin an active state; detecting, on a second OFDM symbol of the grant freetransmission resource, a second pilot sequence that is sent by theterminal device and that corresponds to the first pilot sequence, wherethe second pilot sequence is used for uplink data demodulation; anddemodulating uplink data according to the second pilot sequence.

With reference to the second aspect, in a first possible implementationof the second aspect, the detecting, on a first orthogonal frequencydivision multiplexing OFDM symbol of a grant free transmission resource,a first pilot sequence sent by a terminal device includes: detecting thefirst pilot sequence in a part of a subband of the first OFDM symbol ofthe grant free transmission resource.

With reference to the first possible implementation of the secondaspect, in a second possible implementation of the second aspect, anelement of the first pilot sequence is a non-zero element.

With reference to the first possible implementation of the secondaspect, in a third possible implementation of the second aspect, thefirst pilot sequence includes a first pilot sub-sequence and a secondpilot sub-sequence, each element of the first pilot sub-sequence is azero element, and an element of the second pilot sub-sequence is anon-zero element.

With reference to any one of the first to the third possibleimplementations of the second aspect, in a fourth possibleimplementation of the second aspect, the detecting, on a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource, a first pilot sequence sent by a terminal deviceincludes: detecting the first pilot sequence in a first subband of thefirst OFDM symbol of the grant free transmission resource, where thefirst subband includes M resource elements REs, a non-zero symbol formedafter the non-zero element is mapped is an M-order Walsh code, and M isa positive integer and is an exponential power of 2.

With reference to the fourth possible implementation of the secondaspect, in a fifth possible implementation of the second aspect, the REsincluded in the first subband are M consecutive REs.

With reference to any one of the second aspect or the first to the fifthpossible implementations of the second aspect, in a sixth possibleimplementation of the second aspect, the first pilot sequence is inone-to-one correspondence with the second pilot sequence.

With reference to the sixth possible implementation of the secondaspect, in a seventh possible implementation of the second aspect, thesecond pilot sequence is a sub-sequence combination including multiplesub-sequences.

With reference to the seventh possible implementation of the secondaspect, in an eighth possible implementation of the second aspect, atleast two of the multiple sub-sequences included in the second pilotsequence are sub-sequences mapped to a same second OFDM symbol of thegrant free transmission resource.

With reference to the eighth possible implementation of the secondaspect, in a ninth possible implementation of the second aspect, all themultiple sub-sequences included in the second pilot sequence aresub-sequences mapped to a same second OFDM symbol of the grant freetransmission resource.

With reference to the eighth possible implementation of the secondaspect, in a tenth possible implementation of the second aspect, atleast two of the multiple sub-sequences included in the second pilotsequence are sub-sequences separately mapped to different subbands of asame second OFDM symbol of the grant free transmission resource.

With reference to the seventh possible implementation of the secondaspect, in an eleventh possible implementation of the second aspect, allthe multiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to different second OFDM symbols of thegrant free transmission resource.

With reference to the eleventh possible implementation of the secondaspect, in a twelfth possible implementation of the second aspect, allthe multiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to entire frequency bands of thedifferent second OFDM symbols of the grant free transmission resource,and the second OFDM symbols are different from the first OFDM symbol.

With reference to any one of the seventh to the twelfth possibleimplementations of the second aspect, in a thirteenth possibleimplementation of the second aspect, the second pilot sequence isrepresented by multiple cyclic shift values, and the multiple cyclicshift values are in one-to-one correspondence with the multiplesub-sequences.

With reference to any one of the second aspect or the first to thethirteenth possible implementations of the second aspect, in afourteenth possible implementation of the second aspect, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains.

With reference to any one of the second aspect or the first to thefourteenth possible implementations of the second aspect, in a fifteenthpossible implementation of the second aspect, the method is applied todevice-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

According to a third aspect, a pilot sequence transmission apparatus isprovided, where the apparatus includes: a first determining module,configured to determine a first pilot sequence used to indicate whethera terminal device is in an active state; a second determining module,configured to determine a second pilot sequence used for uplink datademodulation; a first mapping module, configured to map the first pilotsequence determined by the first determining module to a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource; a second mapping module, configured to map thesecond pilot sequence determined by the second determining module to asecond OFDM symbol of the grant free transmission resource; and asending module, configured to send the first pilot sequence and thesecond pilot sequence by using the first OFDM symbol mapped by the firstmapping module and the second OFDM symbol mapped by the second mappingmodule.

With reference to the third aspect, in a first possible implementationof the third aspect, the apparatus further includes a third determiningmodule, configured to determine a first pilot number; the firstdetermining module is specifically configured to determine the firstpilot sequence according to the first pilot number; and the seconddetermining module is specifically configured to determine the secondpilot sequence according to the first pilot number.

With reference to the first possible implementation of the third aspect,in a second possible implementation of the third aspect, the thirddetermining module is specifically configured to: determine the firstpilot number according to an identifier of the terminal device; ordetermine the first pilot number according to an identifier of the grantfree transmission resource and an identifier of the terminal device; orgenerate the first pilot number by using a random number generator.

With reference to the third aspect, or the first or the second possibleimplementation of the third aspect, in a third possible implementationof the third aspect, the first mapping module is specifically configuredto map the first pilot sequence to a part of a subband of the first OFDMsymbol of the grant free transmission resource.

With reference to the third possible implementation of the third aspect,in a fourth possible implementation of the third aspect, an element ofthe first pilot sequence is a non-zero element.

With reference to the third possible implementation of the third aspect,in a fifth possible implementation of the third aspect, the first pilotsequence includes a first pilot sub-sequence and a second pilotsub-sequence, each element of the first pilot sub-sequence is a zeroelement, and an element of the second pilot sub-sequence is a non-zeroelement.

With reference to any one of the third to the fifth possibleimplementations of the third aspect, in a sixth possible implementationof the third aspect, the first mapping module is specifically configuredto map the non-zero element included in the first pilot sequence to afirst subband of the first OFDM symbol of the grant free transmissionresource, where the first subband includes M resource elements REs, anon-zero symbol formed after the non-zero element is mapped is anM-order Walsh code, and M is a positive integer and is an exponentialpower of 2.

With reference to the sixth possible implementation of the third aspect,in a seventh possible implementation of the third aspect, the REsincluded in the first subband are M consecutive REs.

With reference to any one of the third aspect or the first to theseventh possible implementations of the third aspect, in an eighthpossible implementation of the third aspect, the first mapping module isspecifically configured to: repeatedly map the first pilot sequence todifferent first OFDM symbols of the grant free transmission resource;and/or repeatedly map the first pilot sequence to different subbands ofthe first OFDM symbol of the grant free transmission resource.

With reference to any one of the third aspect or the first to the eighthpossible implementations of the third aspect, in a ninth possibleimplementation of the third aspect, the first pilot sequence is inone-to-one correspondence with the second pilot sequence.

With reference to the ninth possible implementation of the third aspect,in a tenth possible implementation of the third aspect, the second pilotsequence is a sub-sequence combination including multiple sub-sequences.

With reference to the tenth possible implementation of the third aspect,in an eleventh possible implementation of the third aspect, the secondmapping module is specifically configured to map at least two of themultiple sub-sequences included in the second pilot sequence to a samesecond OFDM symbol of the grant free transmission resource.

With reference to the eleventh possible implementation of the thirdaspect, in a twelfth possible implementation of the third aspect, thesecond mapping module is specifically configured to map all the multiplesub-sequences included in the second pilot sequence to a same secondOFDM symbol of the grant free transmission resource.

With reference to the eleventh possible implementation of the thirdaspect, in a thirteenth possible implementation of the third aspect, thesecond mapping module is specifically configured to separately map atleast two of the multiple sub-sequences included in the second pilotsequence to different subbands of a same second OFDM symbol of the grantfree transmission resource.

With reference to the tenth possible implementation of the third aspect,in a fourteenth possible implementation of the third aspect, the secondmapping module is specifically configured to separately map all themultiple sub-sequences included in the second pilot sequence todifferent second OFDM symbols of the grant free transmission resource.

With reference to the fourteenth possible implementation of the thirdaspect, in a fifteenth possible implementation of the third aspect, thesecond mapping module is specifically configured to separately map allthe multiple sub-sequences included in the second pilot sequence toentire frequency bands of the different second OFDM symbols of the grantfree transmission resource, where the second OFDM symbols are differentfrom the first OFDM symbol.

With reference to any one of the tenth to the fifteenth possibleimplementations of the third aspect, in a sixteenth possibleimplementation of the third aspect, the second pilot sequence isgenerated by using multiple cyclic shift values, and the multiple cyclicshift values are in one-to-one correspondence with the multiplesub-sequences.

With reference to any one of the third aspect or the first to thesixteenth possible implementations of the third aspect, in a seventeenthpossible implementation of the third aspect, the second mapping moduleis specifically configured to repeatedly map the second pilot sequenceto different second OFDM symbols of the grant free transmissionresource.

With reference to any one of the third aspect or the first to theseventeenth possible implementations of the third aspect, in aneighteenth possible implementation of the third aspect, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains.

With reference to any one of the third aspect or the first to theeighteenth possible implementations of the third aspect, in a nineteenthpossible implementation of the third aspect, the first determiningmodule is specifically configured to select the first pilot sequencefrom a first pilot sequence set.

With reference to any one of the third aspect or the first to thenineteenth possible implementations of the third aspect, in a twentiethpossible implementation of the third aspect, the second determiningmodule is specifically configured to select the second pilot sequencefrom a second pilot sequence set.

With reference to any one of the third aspect or the first to thetwentieth possible implementations of the third aspect, in atwenty-first possible implementation of the third aspect, the method isapplied to device-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

With reference to any one of the third aspect or the first to thetwenty-first possible implementations of the third aspect, in atwenty-second possible implementation of the third aspect, the apparatusis a terminal device.

According to a fourth aspect, a pilot sequence transmission apparatus isprovided, where the apparatus includes: a first detection module,configured to detect, on a first orthogonal frequency divisionmultiplexing OFDM symbol of a grant free transmission resource, a firstpilot sequence sent by a terminal device, where the first pilot sequenceis used to indicate whether the terminal device is in an active state; asecond detection module, configured to detect, on a second OFDM symbolof the grant free transmission resource, a second pilot sequence that issent by the terminal device and that corresponds to the first pilotsequence detected by the first detection module, where the second pilotsequence is used for uplink data demodulation; and a processing module,configured to demodulate uplink data according to the second pilotsequence detected by the second detection module.

With reference to the fourth aspect, in a first possible implementationof the fourth aspect, the first detection module is specificallyconfigured to detect the first pilot sequence in a part of a subband ofthe first OFDM symbol of the grant free transmission resource.

With reference to the first possible implementation of the fourthaspect, in a second possible implementation of the fourth aspect, anelement of the first pilot sequence is a non-zero element.

With reference to the first possible implementation of the fourthaspect, in a third possible implementation of the fourth aspect, thefirst pilot sequence includes a first pilot sub-sequence and a secondpilot sub-sequence, each element of the first pilot sub-sequence is azero element, and an element of the second pilot sub-sequence is anon-zero element.

With reference to any one of the first to the third possibleimplementations of the fourth aspect, in a fourth possibleimplementation of the fourth aspect, the first detection module isspecifically configured to detect the first pilot sequence in a firstsubband of the first OFDM symbol of the grant free transmissionresource, where the first subband includes M resource elements REs, anon-zero symbol formed after the non-zero element is mapped is anM-order Walsh code, and M is a positive integer and is an exponentialpower of 2.

With reference to the fourth possible implementation of the fourthaspect, in a fifth possible implementation of the fourth aspect, the REsincluded in the first subband are M consecutive REs.

With reference to any one of the fourth aspect or the first to the fifthpossible implementations of the fourth aspect, in a sixth possibleimplementation of the fourth aspect, the first pilot sequence is inone-to-one correspondence with the second pilot sequence.

With reference to the sixth possible implementation of the fourthaspect, in a seventh possible implementation of the fourth aspect, thesecond pilot sequence is a sub-sequence combination including multiplesub-sequences.

With reference to the seventh possible implementation of the fourthaspect, in an eighth possible implementation of the fourth aspect, atleast two of the multiple sub-sequences included in the second pilotsequence are sub-sequences mapped to a same second OFDM symbol of thegrant free transmission resource.

With reference to the eighth possible implementation of the fourthaspect, in a ninth possible implementation of the fourth aspect, all themultiple sub-sequences included in the second pilot sequence aresub-sequences mapped to a same second OFDM symbol of the grant freetransmission resource.

With reference to the eighth possible implementation of the fourthaspect, in a tenth possible implementation of the fourth aspect, atleast two of the multiple sub-sequences included in the second pilotsequence are sub-sequences separately mapped to different subbands of asame second OFDM symbol of the grant free transmission resource.

With reference to the seventh possible implementation of the fourthaspect, in an eleventh possible implementation of the fourth aspect, allthe multiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to different second OFDM symbols of thegrant free transmission resource.

With reference to the eleventh possible implementation of the fourthaspect, in a twelfth possible implementation of the fourth aspect, allthe multiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to entire frequency bands of thedifferent second OFDM symbols of the grant free transmission resource,and the second OFDM symbols are different from the first OFDM symbol.

With reference to any one of the seventh to the twelfth possibleimplementations of the fourth aspect, in a thirteenth possibleimplementation of the fourth aspect, the second pilot sequence isrepresented by multiple cyclic shift values, and the multiple cyclicshift values are in one-to-one correspondence with the multiplesub-sequences.

With reference to any one of the fourth aspect or the first to thethirteenth possible implementations of the fourth aspect, in afourteenth possible implementation of the fourth aspect, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains.

With reference to any one of the fourth aspect or the first to thefourteenth possible implementations of the fourth aspect, in a fifteenthpossible implementation of the fourth aspect, the method is applied todevice-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

With reference to any one of the fourth aspect or the first to thefifteenth possible implementations of the fourth aspect, in a sixteenthpossible implementation of the fourth aspect, the apparatus is a networkdevice.

Based on the foregoing technical solutions, in the pilot sequencetransmission method and apparatus in the embodiments of the presentinvention, a terminal device determines a first pilot sequence used toindicate whether the terminal device is in an active state anddetermines a second pilot sequence used for uplink data demodulation,respectively maps the first pilot sequence and the second pilot sequenceto a first OFDM symbol and a second OFDM symbol of a grant freetransmission resource, and sends the first pilot sequence and the secondpilot sequence by using the first OFDM symbol and the second OFDMsymbol. Therefore, a network device can determine activeness of theterminal device by detecting the first pilot sequence, and can detectonly a second pilot sequence of a terminal device that is in an activestate, and does not need to detect all possible second pilot sequences,so that a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly describes the accompanyingdrawings required for describing the embodiments of the presentinvention. Apparently, the accompanying drawings in the followingdescription show merely some embodiments of the present invention, and aperson of ordinary skill in the art may still derive other drawings fromthese accompanying drawings without creative efforts.

FIG. 1 is a schematic diagram of an application scenario according to anembodiment of the present invention;

FIG. 2 is a schematic block diagram of a pilot sequence transmissionmethod according to an embodiment of the present invention;

FIG. 3 is another schematic block diagram of a pilot sequencetransmission method according to an embodiment of the present invention;

FIG. 4A to FIG. 4C are separately schematic diagrams showingdistribution of a first pilot sequence on a time-frequency resourceaccording to an embodiment of the present invention;

FIG. 5A to FIG. 5F are separately schematic diagrams showingdistribution of a second pilot sequence on a time-frequency resourceaccording to an embodiment of the present invention;

FIG. 6 is a schematic block diagram of a pilot sequence transmissionmethod according to another embodiment of the present invention;

FIG. 7 is a schematic block diagram of a pilot sequence transmissionapparatus according to an embodiment of the present invention;

FIG. 8 is another schematic block diagram of a pilot sequencetransmission apparatus according to an embodiment of the presentinvention;

FIG. 9 is a schematic block diagram of a pilot sequence transmissionapparatus according to another embodiment of the present invention;

FIG. 10 is a schematic block diagram of a pilot sequence transmissionapparatus according to still another embodiment of the presentinvention; and

FIG. 11 is a schematic block diagram of a pilot sequence transmissionapparatus according to still another embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

The following clearly describes the technical solutions in theembodiments of the present invention with reference to the accompanyingdrawings in the embodiments of the present invention. Apparently, thedescribed embodiments are a part rather than all of the embodiments ofthe present invention. All other embodiments obtained by a person ofordinary skill in the art based on the embodiments of the presentinvention without creative efforts shall fall within the protectionscope of the present invention.

It should be understood that, in a current cellular communicationssystem, for example, a Global System for Mobile Communications (GSM)system, a Wideband Code Division Multiple Access (WCDMA) system, or aLong Term Evolution (LTE) system, supported communication is mainlyvoice communication and data communication. Usually, a quantity ofconnections supported by a conventional base station is limited, and iseasy to be implemented.

A next-generation mobile communications system not only supportsconventional voice communication and data communication, but alsosupports machine to machine (M2M) communication that is also referred toas machine type communication (MTC). According to prediction, by 2020, aquantity of MTC devices connected to networks may reach 50 to 100billion, and this may far exceed a current quantity of connections.

For an MTC type service, because service types of the MTC type servicediffer from each other, network requirements differ greatly. Generally,there may be two services having the following requirements: One is aservice that requires reliable transmission but is not sensitive to adelay, and the other is a service that requires a low delay andhigh-reliability transmission. It is relatively easy to process theservice that requires reliable transmission but is not sensitive to adelay. However, for the service that requires a low delay andhigh-reliability transmission, if transmission is unreliable,retransmission is caused and an excessively large transmission delay iscaused, and consequently, the requirements cannot be satisfied.

Because there are a large quantity of connections, a future wirelesscommunications system greatly differs from an existing communicationssystem. The large quantity of connections need to consume more resourcesto connect to terminal devices, and need to consume more resources totransmit scheduling signaling related to data transmission of theterminal devices.

FIG. 1 is a schematic diagram of a communications system to which theembodiments of the present invention are applied. As shown in FIG. 1, anetwork 100 includes a network device 102 and terminal devices 104, 106,108, 110, 112, and 114 (briefly referred to as UE in the figure). Thenetwork device is connected to the terminal devices in a wired manner ora wireless manner or another manner. It should be understood that in anexample of FIG. 1 for description, the network includes only one networkdevice, but the embodiments of the present invention are not limitedthereto. For example, the network may further include more networkdevices. Similarly, the network may further include more terminaldevices, and the network device may further include another device.

The network in the embodiments of the present invention may be a publicland mobile network (PLMN), a device-to-device (D2D) network, an M2Mnetwork, or another network. FIG. 1 is merely an example of a simplifiedschematic diagram. The network may further include another networkdevice not shown in FIG. 1.

The terminal device in the embodiments of the present invention may beuser equipment (UE), an access terminal, a subscriber unit, a subscriberstation, a mobile site, a mobile station, a remote site, a remoteterminal, a mobile device, a user terminal, a terminal, a wirelesscommunications device, a user agent, or a user apparatus. The accessterminal may be a cellular phone, a cordless phone, a Session InitiationProtocol (SIP) phone, a wireless local loop (WLL) site, a personaldigital assistant (PDA), a handheld device having a wirelesscommunications function, a computing device or another processing deviceconnected to a wireless modem, a vehicle-mounted device, a wearabledevice, a terminal device in a future 5G network, a terminal device in afuture evolved PLMN network, or the like.

The network device in the embodiments of the present invention may be adevice configured to communicate with the terminal device. The networkdevice may be a base station transceiver station (BTS) in GSM or codedivision multiple access (CDMA), or may be a NodeB (NB) in a widebandcode division multiple access (WCDMA) system, or may be an evolved NodeB(eNB or eNodeB) in a Long Term Evolution (LTE) system, or may be a radiocontroller in a cloud radio access network (CRAN) scenario, or thenetwork device may be a relay site, an access point, a vehicle-mounteddevice, a wearable device, a network device in a future 5G network, anetwork device in a future evolved PLMN network, or the like.

To handle a large quantity of MTC type services in a future network andsatisfy low-delay and high-reliability service transmission, this patentproposes a grant free transmission solution. English for grant freetransmission may be represented by grant free. The grant freetransmission herein may be for uplink data transmission. The grant freetransmission may be understood as any one of or more of the followingmeanings, or a combination of partial technical features of multiplemeanings, or another similar meaning.

Grant free transmission may be: A network device pre-allocates multipletransmission resources to a terminal device and notify the terminaldevice of the multiple transmission resources; when having an uplinkdata transmission requirement, the terminal device selects at least onetransmission resource from the multiple transmission resourcespre-allocated by the network device, and sends uplink data by using theselected transmission resource; and the network device detects, on oneor more transmission resources in the pre-allocated multipletransmission resources, the uplink data sent by the terminal device. Thedetection may be blind detection, or may be detection performedaccording to a particular control field in the uplink data, or detectionperformed in another manner.

Grant free transmission may be: A network device pre-allocates multipletransmission resources to a terminal device and notify the terminaldevice of the multiple transmission resources, so that when having anuplink data transmission requirement, the terminal device selects atleast one transmission resource from the multiple transmission resourcespre-allocated by the network device, and sends uplink data by using theselected transmission resource.

Grant free transmission may be: Information about multiple pre-allocatedtransmission resources is obtained, and when uplink data transmission isrequired, at least one transmission resource is selected from themultiple transmission resources, and uplink data is sent by using theselected transmission resource. The information may be obtained from anetwork device.

Grant free transmission may be a method for transmitting uplink data bya terminal device without dynamic scheduling of a network device. Thedynamic scheduling may be a scheduling manner in which the networkdevice indicates a transmission resource for the terminal device byusing signaling in each time of uplink data transmission. Optionally,transmitting uplink data by the terminal device may be understood as:Two or more terminal devices are allowed to transmit uplink data on asame time-frequency resource. Optionally, the transmission resource maybe a transmission resource in one or more transmission time units aftera moment at which UE receives the signaling. One transmission time unitmay be a smallest time unit of one time of transmission, for example, atransmission time interval (TTI), and a value may be 1 ms.Alternatively, one transmission time unit may be a preset transmissiontime unit.

Grant free transmission may be: A terminal device transmits uplink datawithout a grant of a network device. The grant may be: The terminaldevice sends an uplink scheduling request to the network device, andafter receiving the scheduling request, the network device sends anuplink grant to the terminal device. The uplink grant indicates anuplink transmission resource allocated to the terminal device.

Grant free transmission may be a contention transmission manner, andspecifically, may be: Multiple terminals transmit uplink data on a samepre-allocated time-frequency resource at the same time without a grantof a base station.

The data may include service data or signaling data.

The blind detection may be understood as: When whether data arrives isnot known in advance, data that may arrive is detected. The blinddetection may be understood as detection without explicit signalingindication.

The transmission resource may include but is not limited to one of or acombination of multiple of the following resources:

-   -   a time domain resource, for example, a radio frame, a subframe,        or a symbol;    -   a frequency domain resource, for example, a subcarrier or a        resource block;    -   a spatial domain resource, for example, a transmit antenna or a        beam;    -   a code domain resource, for example, a sparse code multiple        access (SCMA) code book, a low density signature (LDS) sequence,        or a CDMA code; or    -   an uplink pilot resource.

Transmission of the foregoing transmission resource may include but isnot limited to the following control mechanisms:

-   -   uplink power control, for example, control of an upper limit of        uplink transmit power;    -   modulation and coding scheme setting, for example, transport        block size setting, bit rate setting, or modulation order        setting; and    -   a retransmission mechanism, for example, an HARQ mechanism.

A contention transmission unit (CTU) may be a basic transmissionresource for grant free transmission. The CTU may be a transmissionresource combining time, frequency, and code domains, or may be atransmission resource combining time, frequency, and a pilot, or may bea transmission resource combining time, frequency, code domain, and apilot.

An access region of the CTU may be a time-frequency region used forgrant free transmission, and may further be a time-frequency regioncorresponding to the CTU.

A patent application No. PCT/CN2014/073084 and entitled “SYSTEM ANDMETHOD FOR UPLINK GRANT-FREE TRANSMISSION SCHEME” has given a technicalsolution of uplink grant free transmission. In the applicationPCT/CN2014/073084, wireless resources may be divided into various CTUs,and UE is mapped to a particular CTU. A group of code may be allocatedto each CTU, and the allocated group of code may be a group of CDMAcode, or may be an SCMA code book set, an LDS sequence group, asignature group, or the like. Each code may correspond to one group ofpilots. A user may select a code and a pilot in a pilot groupcorresponding to the code, to perform uplink transmission. It may beunderstood that application content of PCT/CN2014/073084 may beincorporated as a part of content of the embodiments of the presentinvention by reference, and details are not described herein.

An application scenario of the embodiments of the present invention isdescribed above with reference to FIG. 1. In the following, a pilotsequence transmission method in the embodiments of the present inventionis described from a terminal device side with reference to FIG. 2 toFIG. 4F.

FIG. 2 shows a pilot sequence transmission method 200 according to anembodiment of the present invention. The method 200, for example, may beperformed by a terminal device. As shown in FIG. 2, the method 200includes the following steps.

S210: Determine a first pilot sequence used to indicate whether theterminal device is in an active state. Optionally, the determining afirst pilot sequence used to indicate whether the terminal device is inan active state may be: selecting, by the terminal device, the firstpilot sequence from a first pilot sequence set, or may be: determining,by the terminal device, the first pilot sequence by means of calculationaccording to a formula or in another manner.

S220: Determine a second pilot sequence used for uplink datademodulation. Optionally, the determining a second pilot sequence usedfor uplink data demodulation may be: selecting the second pilot sequencefrom a second pilot sequence set, or may be: determining, by theterminal device, the second pilot sequence by means of calculationaccording to a formula or in another manner.

S230: Map the first pilot sequence to a first orthogonal frequencydivision multiplexing OFDM symbol of a grant free transmission resource.

S240: Map the second pilot sequence to a second OFDM symbol of the grantfree transmission resource.

S250: Send the first pilot sequence and the second pilot sequence byusing the first OFDM symbol and the second OFDM symbol.

Specifically, in a grant free transmission system, there are a largequantity of terminal devices, but at the same time, there are anextremely small quantity of terminal devices that access a network, thatis, an extremely small quantity of terminal devices are in an activestate. Because the terminal device may randomly select a grant freetransmission resource to send data, a network device does not know inadvance which terminal devices are terminal devices that are in anactive state. Therefore, the network device needs to detect everypossible pilot, to determine a terminal device that is in an activestate. Complexity of this detection process is extremely high.

To reduce pilot detection complexity of the network device, in a grantfree access process of the terminal device, the terminal device mayselect the grant free transmission resource. For example, the terminaldevice may select a CTU. To transmit uplink data, the terminal devicemay determine the first pilot sequence and the second pilot sequence.The first pilot sequence is used to indicate a status of the terminaldevice, for example, used to indicate whether the terminal device is inan active state. The second pilot sequence is used for uplink datademodulation. Specifically, it may be understood that the second pilotsequence is used for channel estimation, so that uplink data isdemodulated according to a channel estimation result. Further, theterminal device may respectively map the first pilot sequence and thesecond pilot sequence to the first OFDM symbol and the second OFDMsymbol of the grant free transmission resource, and send the first pilotsequence and the second pilot sequence by using the first OFDM symboland the second OFDM symbol.

Correspondingly, the network device may detect the first pilot sequenceon the first OFDM symbol. When the network device detects the firstpilot sequence, the network device may determine that the terminaldevice sending the first pilot sequence is in an active state, so thatthe network device may detect, on the second OFDM symbol, only thesecond pilot sequence corresponding to the first pilot sequence. Thatis, the network device may detect only the second pilot sequence of theterminal device that is in an active state, and may perform channelestimation according to the second pilot sequence and further demodulateuplink data according to a channel estimation result, and the networkdevice does not need to detect all possible second pilot sequences, sothat a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

Therefore, in the pilot sequence transmission method in this embodimentof the present invention, a terminal device determines a first pilotsequence used to indicate whether the terminal device is in an activestate and determines a second pilot sequence used for uplink datademodulation, respectively maps the first pilot sequence and the secondpilot sequence to a first OFDM symbol and a second OFDM symbol of agrant free transmission resource, and sends the first pilot sequence andthe second pilot sequence by using the first OFDM symbol and the secondOFDM symbol. Therefore, a network device can determine activeness of theterminal device by detecting the first pilot sequence, and can detectonly a second pilot sequence of a terminal device that is in an activestate, and does not need to detect all possible second pilot sequences,so that a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

It should be understood that, in this embodiment of the presentinvention, a pilot sequence may be briefly referred to as a pilot or apilot signal, or may be referred to as a reference signal (RS).Correspondingly, pilot sequence transmission may also be understood aspilot transmission or reference signal transmission. This embodiment ofthe present invention is described merely by using a pilot sequence asan example, but the present invention is not limited thereto.

It should be understood that, in this embodiment of the presentinvention, the first pilot sequence is used to indicate the status ofthe terminal device, that is, used to indicate a status of the terminaldevice that transmits the first pilot sequence. For example, the firstpilot sequence is used to indicate whether the terminal device is in anactive state. For another example, whether the terminal device sends thefirst pilot sequence may be used to indicate whether the terminal deviceis in an active state. The first pilot sequence may be a Walsh code, ormay be another pilot sequence used by the network device to determineactiveness or an active state of the terminal device. For example, thefirst pilot sequence is a Zadoff-Chu (ZC) sequence. For another example,the first pilot sequence is an activity detection reference signal(ADRS), but this embodiment of the present invention is not limitedthereto.

It should be further understood that, in this embodiment of the presentinvention, the second pilot sequence is used for uplink datademodulation. Specifically, the second pilot sequence may be used by thenetwork device for channel estimation, so that the network devicedemodulates uplink data sent by the terminal device. The second pilotsequence is, for example, a DMRS. Certainly, the second pilot sequencemay be another pilot sequence used by the network device for uplink datademodulation, and this embodiment of the present invention is notlimited thereto.

It should be further understood that, in this embodiment of the presentinvention, the grant free transmission resource may represent atime-frequency resource used to transmit data in grant freetransmission, or the grant free transmission resource may represent atransmission resource combining time, frequency, and code domains ingrant free transmission, or another transmission resource describedabove. For example, the grant free transmission resource is a CTU accessregion. It should be further understood that this embodiment of thepresent invention is described merely by using a CTU access region as anexample, but the present invention is not limited thereto.

It should be further understood that, in this embodiment of the presentinvention, the first OFDM symbol is an OFDM symbol used to transmit thefirst pilot sequence in the grant free transmission resource. Therefore,the first OFDM symbol may also be referred to as a first pilot symbol.One grant free transmission resource may include one or more first OFDMsymbols. The second OFDM symbol is an OFDM symbol used to transmit thesecond pilot sequence in the grant free transmission resource.Therefore, the second OFDM symbol may also be referred to as a secondpilot symbol. One grant free transmission resource may include one ormore second OFDM symbols. The first OFDM symbol and the second OFDMsymbol may be completely the same, or may be completely different, ormay have some same OFDM symbols. For example, the same OFDM symbols ofthe first OFDM symbol and the second OFDM symbol may not only be used totransmit the first pilot sequence, but may also be used to transmit thesecond pilot sequence.

In this embodiment of the present invention, as shown in FIG. 3,optionally, the method 200 further includes:

S260: Determine a first pilot number.

The determining a first pilot sequence used to indicate whether aterminal device is in an active state includes:

S211: Determine the first pilot sequence according to the first pilotnumber.

The determining a second pilot sequence used for uplink datademodulation includes:

S221: Determine the second pilot sequence according to the first pilotnumber.

That is, in this embodiment of the present invention, in a grant freeaccess process of the terminal device, the terminal device may selectthe grant free transmission resource. For example, the terminal devicemay select a CTU access region. To transmit uplink data, the terminaldevice may determine the first pilot number, and may thereby determinethe first pilot sequence according to the first pilot number, anddetermine the second pilot sequence according to the first pilot number.That is, there is a correspondence between the first pilot sequence andthe second pilot sequence. Further, the terminal device may respectivelymap the first pilot sequence and the second pilot sequence to the firstOFDM symbol and the second OFDM symbol of the grant free transmissionresource, and send the first pilot sequence and the second pilotsequence by using the first OFDM symbol and the second OFDM symbol.

Therefore, in the pilot sequence transmission method in this embodimentof the present invention, a terminal device determines a first pilotnumber, determines a first pilot sequence and a second pilot sequenceaccording to the first pilot number, respectively maps the first pilotsequence and the second pilot sequence to a first OFDM symbol and asecond OFDM symbol of a grant free transmission resource, and sends thefirst pilot sequence and the second pilot sequence by using the firstOFDM symbol and the second OFDM symbol. Therefore, a network device candetermine activeness of the terminal device by detecting the first pilotsequence, and can detect only the second pilot sequence corresponding tothe first pilot sequence, and does not need to detect all possiblesecond pilot sequences, so that a quantity of detected pilots can besignificantly reduced, and pilot detection complexity is reduced.

It should be understood that this embodiment of the present invention isdescribed merely by using an example in which the terminal devicedetermines the first pilot sequence and the second pilot sequenceaccording to the first pilot number, but the present invention is notlimited thereto. For example, the terminal device may select a firstpilot sequence from a first pilot sequence set, or the terminal devicemay select a second pilot sequence from a second pilot sequence set. Foranother example, the terminal device may select a first pilot sequencefrom a first pilot sequence set, and may thereby determine a secondpilot sequence corresponding to the first pilot sequence. For anotherexample, the terminal device may determine a first pilot sequence and acorresponding second pilot sequence in a correspondence table of a firstpilot sequence and a second pilot sequence. For another example, theterminal device may determine a first pilot sequence according to aformula, and determine a corresponding second pilot sequence accordingto a correspondence between a first pilot sequence and a second pilotsequence.

It should be understood that, in this embodiment of the presentinvention, optionally, the terminal device may determine the first pilotsequence used to indicate whether the terminal device is in an activestate, and determine, according to a correspondence between the firstpilot sequence and the second pilot sequence, the second pilot sequenceused for uplink data demodulation. Therefore, the terminal device mayrespectively map the first pilot sequence and the second pilot sequenceto the first OFDM symbol and the second OFDM symbol of the grant freetransmission resource, and send the first pilot sequence and the secondpilot sequence by using the first OFDM symbol and the second OFDMsymbol.

It should be further understood that sequence numbers of the foregoingprocesses do not mean execution sequences in various embodiments of thepresent invention. Execution sequences of the processes need to bedetermined according to functions and internal logic of the processes,and should not be construed as any limitation to implementationprocesses of the embodiments of the present invention.

In the following, the pilot sequence transmission method in thisembodiment of the present invention is further described in detail withreference to FIG. 4A to FIG. 5F.

In S260, the terminal device determines the first pilot number.Specifically, for example, the terminal device may determine a pilotnumber in various manners, for example, by means of calculation,selection (for example, random selection), or table searching, oraccording to a system configuration parameter.

Optionally, in this embodiment of the present invention, the determininga first pilot number includes:

determining the first pilot number according to an identifier of theterminal device; or

determining the first pilot number according to an identifier of thegrant free transmission resource and an identifier of the terminaldevice; or

generating the first pilot number by using a random number generator.

Specifically, in this embodiment of the present invention, the terminaldevice may determine the first pilot number according to the identifierof the terminal device. For example, the terminal device may use, as thefirst pilot number, a value that is obtained after 1 is added to aresult of performing a modulo operation on a total quantity of terminaldevices or a total quantity of first pilot sequences according to theidentifier ID of the terminal device, or use, as the first pilot number,a value that is obtained after another operation is performed accordingto the ID of the terminal device. The identifier of the terminal devicemay be a subscriber identity inside a cell, for example, a cell radionetwork temporary identity (C-RNTI). Alternatively, the identifier ofthe terminal device may be a global subscriber identity, for example, aninternational mobile subscriber identity (IMSI) or a temporary mobilesubscriber identity (TMSI).

It should be understood that this embodiment of the present invention isdescribed merely by using the C-RNTI, the IMSI, and the TMSI as anexample, but the present invention is not limited thereto. Theidentifier of the terminal device used to determine the first pilotnumber may be another subscriber identity. The present invention doesnot limit a specific method for determining the first pilot numberaccording to the identifier of the terminal device. For example, theterminal device may determine the first pilot number according to acorrespondence between an identifier of the terminal device and a pilotnumber. The correspondence between an identifier of the terminal deviceand a pilot number may be represented by a table, an algorithm, aformula, or the like.

In this embodiment of the present invention, the terminal device mayfurther determine the first pilot number according to the identifier ofthe grant free transmission resource and the identifier of the terminaldevice. That is, when selecting different grant free transmissionresources, a same terminal device may have different first pilotnumbers. It should be further understood that this embodiment of thepresent invention is described merely by using this as an example, butthe present invention is not limited thereto. For example, the terminaldevice may determine the first pilot number with reference to anotherfactor. In another aspect, in this embodiment of the present invention,the terminal device may generate the first pilot number by using therandom number generator, but the present invention is not limitedthereto.

For example, in this embodiment of the present invention, the firstpilot number i may be determined by using the following formula (1):i=mod(N _(ID) ,N _(k))  (1), where

mod( ) represents a modulo operation, N_(ID) represents the ID of theterminal device, and N_(k) represents a quantity of first pilotsequences of a k^(th) grant free transmission resource.

It should be understood that this embodiment of the present invention isdescribed merely by using the formula (1) as an example, but the presentinvention is not limited thereto. For example, a sum of a valuedetermined according to the foregoing formula (1) and a determinednatural number may be used as the first pilot number, or a differencebetween a value determined according to the foregoing formula (1) and adetermined natural number may be used as the first pilot number.

In S211, the terminal device determines the first pilot sequenceaccording to the first pilot number. Specifically, in this embodiment ofthe present invention, the terminal device may determine the first pilotsequence according to a correspondence between the first pilot numberand the first pilot sequence. The correspondence may have multiplerepresentation forms, for example, a formula or a table. That is, theterminal device may determine the first pilot sequence by performing anoperation according to a formula, or may determine, by means of tablesearching, the first pilot sequence corresponding to the first pilotnumber. It should be understood that this embodiment of the presentinvention is described merely by using this as an example, but thepresent invention is not limited thereto.

For example, in this embodiment of the present invention, the terminaldevice may determine the first pilot sequence corresponding to the firstpilot number from the first pilot sequence set. Optionally, a quantityof pilot sequences included in the first pilot sequence set is preset.Optionally, the quantity of pilot sequences included in the first pilotsequence set is the same as a quantity of resource elements (RE) used totransmit a pilot sequence in one grant free transmission resource.

For example, in this embodiment of the present invention, it is assumedthat the grant free transmission resource is a contention transmissionunit CTU access region, and for each CTU access region, there are twoOFDM symbols that are used to transmit the first pilot sequence.Further, it is assumed that each OFDM symbol has Q resource elementsREs, and for each CTU access region, the first pilot sequence set mayinclude 2Q first pilot sequences. It should be understood that the firstpilot sequence set may include more or fewer pilot sequences.

In this embodiment of the present invention, optionally, an element ofthe first pilot sequence is a non-zero element. In this embodiment ofthe present invention, because the first pilot sequence is used toindicate activeness of the terminal device, the first pilot sequence maybe designed to have a relatively short length. Therefore, the non-zeroelement may be mapped to a part of a subband of the grant freetransmission resource. That is, the terminal device may send the firstpilot sequence on a part of a frequency resource of an OFDM symbol, anddoes not need to send the first pilot sequence over entire transmissionbandwidth of the OFDM symbol. Therefore, in one aspect, pilot overheadscan be significantly reduced, and in another aspect, a relatively shortfirst pilot sequence facilitates detection performed by the networkdevice, so that pilot detection complexity can be further reduced.

In another aspect, in this embodiment of the present invention,optionally, the first pilot sequence includes a first pilot sub-sequenceand a second pilot sub-sequence. Each element of the first pilotsub-sequence is a zero element, and an element of the second pilotsub-sequence is a non-zero element. The first pilot sequence may bemapped to a part of a subband of the grant free transmission resource,so that pilot overheads can be significantly reduced. Although comparedwith the first pilot sequence in the previous embodiment, the firstpilot sequence in this embodiment has a larger length, each element ofthe first pilot sub-sequence is a zero element, and the first pilotsequence may be mapped into a zero symbol on the grant free transmissionresource. Therefore, pilot detection complexity can also be reduced.

In this embodiment of the present invention, optionally, the non-zeroelement included in the first pilot sequence is mapped to M resourceelements REs of the grant free transmission resource, a non-zero symbolformed after the non-zero element is mapped is an M-order Walsh code,and M is a positive integer and is an exponential power of 2.Optionally, the M REs are M consecutive REs, so that orthogonalitybetween pilot sequences can be further enhanced.

It should be understood that this embodiment of the present invention isdescribed merely by using the Walsh code as an example, but the presentinvention is not limited thereto. For example, the first pilot sequencemay be a pseudo-noise sequence that is also referred to as a PNsequence, or the first pilot sequence may be a Zadoff-Chu (ZC) sequenceor an M sequence.

It should be further understood that, in this embodiment of the presentinvention, if the first pilot sequence is a Zadoff-Chu sequence,terminal devices mapped to a same subband may be distinguished by usingcyclic shift values and root numbers. If the first pilot sequence is anM sequence, terminal devices mapped to a same subband may bedistinguished by using cyclic shift values, that is, first pilotsequences of the terminal devices mapped to the same subband correspondto different cyclic shift values.

Correspondingly, in S230, the terminal device maps the first pilotsequence to the first orthogonal frequency division multiplexing OFDMsymbol of the grant free transmission resource.

It should be understood that, in this embodiment of the presentinvention, the first OFDM symbol is an OFDM symbol used to transmit thefirst pilot sequence in the grant free transmission resource. Therefore,the first OFDM symbol may also be referred to as a first pilot symbol.One grant free transmission resource may include one or more first OFDMsymbols. For example, in this embodiment of the present invention, thegrant free transmission resource is, for example, a CTU access region. Afirst OFDM symbol in one CTU access region may include two OFDM symbols.Further, for example, the first OFDM symbol in the CTU access region mayinclude the third OFDM symbol and the tenth OFDM symbol of the CTUaccess region. It should be further understood that, in this embodimentof the present invention, first OFDM symbols of grant free transmissionresources may include a same quantity of OFDM symbols or differentquantities of OFDM symbols.

It should be further understood that this embodiment of the presentinvention is described merely by using this as an example, but thepresent invention is not limited thereto. For example, a first OFDMsymbol in one CTU access region may include only one OFDM symbol, or afirst OFDM symbol in one CTU access region may include three or moreOFDM symbols.

In this embodiment of the present invention, as shown in FIG. 4A,optionally, the mapping the first pilot sequence to a first orthogonalfrequency division multiplexing OFDM symbol of a grant free transmissionresource includes:

mapping the first pilot sequence to a part of a subband of the firstOFDM symbol of the grant free transmission resource.

Specifically, as shown in FIG. 4A, the terminal device may map the firstpilot sequence to a part of a subband of the third OFDM symbol, and thefirst pilot sequence does not occupy entire transmission bandwidth ofthe OFDM symbol, so that pilot overheads can be significantly reduced.

It should be understood that this embodiment of the present invention isdescribed merely by using an example in which the first pilot sequenceis mapped to four REs, but the present invention is not limited thereto.For example, the first pilot sequence may be mapped to two REs or eightREs. It should be further understood that this embodiment of the presentinvention is described merely by using an example in which the firstpilot sequence is mapped to a part of a subband of one OFDM symbol, butthe present invention is not limited thereto. For example, the firstpilot sequence may be mapped to parts of subbands of two or more OFDMsymbols.

Optionally, in this embodiment of the present invention, an element ofthe first pilot sequence mapped to the part of the subband of the OFDMsymbol may be a non-zero element. Optionally, in this embodiment of thepresent invention, the first pilot sequence mapped to the part of thesubband of the OFDM symbol may include a first pilot sub-sequence and asecond pilot sub-sequence. Each element of the first pilot sub-sequencemay be a zero element, and an element of the second pilot sub-sequencemay be a non-zero element. It should be understood that, in thisembodiment of the present invention, the first pilot sub-sequenceincluding only a zero element is mapped into a zero symbol, and thesecond pilot sub-sequence including a non-zero element is mapped into anon-zero symbol.

Optionally, in this embodiment of the present invention, the mapping thefirst pilot sequence to a first orthogonal frequency divisionmultiplexing OFDM symbol of a grant free transmission resource includes:

mapping the non-zero element included in the first pilot sequence to afirst subband of the first OFDM symbol of the grant free transmissionresource, where the first subband includes M resource elements REs, anon-zero symbol formed after the non-zero element is mapped is anM-order Walsh code, and M is a positive integer and is an exponentialpower of 2.

Optionally, in this embodiment of the present invention, the REsincluded in the first subband are M consecutive REs. That is, in thisembodiment of the present invention, the first pilot sequence ispreferably mapped to consecutive REs of a subband, so that betterorthogonality between different first pilot sequences is achieved, andpilot detection reliability of a system can be further improved.

For example, it is assumed that 144 different first pilot sequences areconfigured for each CTU access region in total, that is, N=144. Nrepresents a quantity of first pilot sequences used for a CTU accessregion. A length of each first pilot sequence is M, and a quantity ofsubcarriers in each CTU access region is K. A sequence whose index is min an M-order Walsh code in the following Table 1, Table 2, or Table 3is determined as a first pilot sequence corresponding to a first pilotnumber i according to the following formula (2):m=mod(mod(i,K),M)  (2), where

i is the first pilot number, 1≤i≤N, m is an integer and 0≤m≤M−1; mod( )is a modulo operator; when M=2, the first pilot sequence correspondingto the first pilot number i is selected from a 2-order Walsh code inTable 1; when M=4, the first pilot sequence corresponding to the firstpilot number i is selected from a 4-order Walsh code in Table 2; whenM=8, the first pilot sequence corresponding to the first pilot number iis selected from an 8-order Walsh code in Table 3.

TABLE 1 (M = 2) m First pilot sequence 0 [+1 +1] 1 [+1 −1]

TABLE 2 (M = 4) m First pilot sequence 0 [+1 +1 +1 +1] 1 [+1 +1 −1 −1] 2[+1 −1 +1 −1] 3 [+1 −1 −1 +1]

TABLE 3 (M = 8) m First pilot sequence 0 [+1 +1 +1 +1 +1 +1 +1 +1] 1 [+1+1 +1 +1 −1 −1 −1 −1] 2 [+1 +1 −1 −1 +1 +1 −1 −1] 3 [+1 +1 −1 −1 −1 −1+1 +1] 4 [+1 −1 +1 −1 −1 +1 −1 +1] 5 [+1 −1 −1 +1 +1 −1 −1 +1] 6 [+1 −1−1 +1 −1 +1 +1 −1] 7 [+1 −1 +1 −1 +1 −1 +1 −1]

For example, when the 2-order Walsh code whose length is 2 is used asthe first pilot sequence, the corresponding first pilot sequence may bedetermined according to the formula (2) and Table 1. Similarly, when the4-order Walsh code whose length is 4 is used as the first pilotsequence, the corresponding first pilot sequence may be determinedaccording to the formula (2) and Table 2, and when the 8-order Walshcode whose length is 8 is used as the first pilot sequence, thecorresponding first pilot sequence may be determined according to theformula (2) and Table 3.

It should be understood that this embodiment of the present invention isdescribed merely by using Table 1 to Table 3 as an example, but thepresent invention is not limited thereto. For example, the first pilotsequence may be a Walsh code of another length, and the first pilotsequence may be another sequence.

For another example, it is assumed that a first OFDM symbol in one CTUaccess region may include the third OFDM symbol and the tenth OFDMsymbol, and an i^(th) first pilot sequence may be mapped to an s^(th) toa t^(th) subcarriers of an a^(th) ADRS pilot symbol in the CTU accessregion according to the following formulas (3) to (5):a=└i/K┘  (3)s=└ mod(i,K)/M┘×M  (4)t=└ mod(i,K)/M┘×M+M−1  (5), where

└ ┘ is a rounding down operator.

It should be understood that this embodiment of the present invention isdescribed merely by using the foregoing formulas as an example, but thepresent invention is not limited thereto. For example, the rounding downoperator in the foregoing formulas may be transformed into a rounding upoperator.

In this embodiment of the present invention, reliability of determininga status of a terminal device is extremely important for a grant freetransmission system. Therefore, reliability of transmitting a firstpilot sequence may be improved by using a diversity technology.

Optionally, as shown in FIG. 4B and FIG. 4C, in this embodiment of thepresent invention, optionally, the mapping the first pilot sequence to afirst orthogonal frequency division multiplexing OFDM symbol of a grantfree transmission resource includes:

repeatedly mapping the first pilot sequence to different first OFDMsymbols of the grant free transmission resource; and/or

repeatedly mapping the first pilot sequence to different subbands of thefirst OFDM symbol of the grant free transmission resource.

For example, as shown in FIG. 4B, same first pilot sequences are sent onthe third OFDM symbol and the tenth OFDM symbol, so that time domaindiversity can be implemented by sending the same first pilot sequences(for example, M-order Walsh codes) on the different first OFDM symbols.Similarly, as shown in FIG. 4C, same first pilot sequences (for example,M-order Walsh codes) are sent in different subbands of the third OFDMsymbol, so that frequency domain diversity can be implemented.

It should be understood that, in this embodiment of the presentinvention, detection reliability can be significantly improved by meansof time domain diversity or frequency domain diversity, but pilotoverheads are increased at the same time. In addition, in thisembodiment of the present invention, detection reliability may beimproved by means of spatial diversity. For example, a quantity ofreceive antennas of a base station may be increased, so that the basestation can separately detect signals received by using multiple receiveantennas, and therefore, detection reliability can be improved withoutincreasing pilot overheads. However, it should be understood that, inthis embodiment of the present invention, a quantity of transmitantennas of the terminal device may be increased. That is, the terminaldevice respectively sends different first pilot sequences on differentantennas. It may be considered that a corresponding terminal device isin an active state provided that the base station detects one of thefirst pilot sequences. In this manner, detection reliability can also beimproved, but pilot overheads need to be increased.

It should be further understood that, in this embodiment of the presentinvention, different first pilot sequences may be distinguished in atleast one of the following three manners: a time domain (an OFDMsymbol), a frequency domain (a subcarrier group or a subband), or a codedomain (a Walsh code or the like). For example, the first pilotsequences may be mapped to a same subband or different subbands ofdifferent OFDM symbols, to distinguish the first pilot sequences.Similarly, the first pilot sequences may be mapped to different subbandsof a same OFDM symbol or different OFDM symbols, to distinguish thefirst pilot sequences. Further, if multiple first pilot sequences aremapped to a same time-frequency resource, different first pilotsequences mapped to the same time-frequency resource need to beorthogonal to each other. In this embodiment of the present invention,preferably, one first OFDM symbol includes multiple groups of resourceelements REs or multiple subbands. Each first pilot sequence ispreferably mapped to one group of REs or one subband of one first OFDMsymbol, and different first pilot sequences on a same group of REs or ina same subband are orthogonal to each other. Further preferably,different first pilot sequences are orthogonal to each other.

Therefore, in the pilot sequence transmission method in this embodimentof the present invention, a terminal device determines a first pilotsequence used to indicate whether the terminal device is in an activestate, maps the first pilot sequence to a first OFDM symbol of a grantfree transmission resource, and sends the first pilot sequence by usingthe first OFDM symbol. Therefore, a network device can determineactiveness of the terminal device by detecting the first pilot sequence,and can detect only a second pilot sequence of a terminal device that isin an active state, and does not need to detect all possible secondpilot sequences, so that a quantity of detected pilots can besignificantly reduced, and pilot detection complexity is reduced.

In S220, the terminal device determines the second pilot sequence usedfor uplink data demodulation. Specifically, the terminal devicedetermines the second pilot sequence corresponding to the first pilotsequence.

For example, in this embodiment of the present invention, the terminaldevice may determine the second pilot sequence according to acorrespondence between the first pilot sequence and the second pilotsequence. The correspondence may have multiple representation forms, forexample, a formula or a table. That is, the terminal device maydetermine the second pilot sequence by performing an operation accordingto a formula, or may determine, by means of table searching, the secondpilot sequence corresponding to the first pilot sequence. It should beunderstood that this embodiment of the present invention is describedmerely by using this as an example, but the present invention is notlimited thereto.

In this embodiment of the present invention, optionally, when thecorrespondence between the first pilot sequence and the second pilotsequence is established by using the first pilot number, that theterminal device determines a second pilot sequence used for uplink datademodulation may include: The terminal device determines the secondpilot sequence according to the first pilot number.

That is, in S221, the terminal device determines the second pilotsequence according to the first pilot number. Specifically, in thisembodiment of the present invention, the terminal device may determinethe second pilot sequence according to a correspondence between thefirst pilot number and the second pilot sequence. The correspondence mayhave multiple representation forms, for example, a formula or a table.That is, the terminal device may determine the second pilot sequence byperforming an operation according to a formula, or may determine, bymeans of table searching, the second pilot sequence corresponding to thefirst pilot number. It should be understood that this embodiment of thepresent invention is described merely by using this as an example, butthe present invention is not limited thereto. For example, in thisembodiment of the present invention, the terminal device may determinethe second pilot sequence corresponding to the first pilot number fromthe second pilot sequence set.

In this embodiment of the present invention, the first pilot sequence isused to indicate a status of the terminal device, and the second pilotsequence is used for uplink data demodulation. There may be acorrespondence between the first pilot sequence and the second pilotsequence. Therefore, the network device may detect, by detecting thefirst pilot sequence, only the second pilot sequence corresponding tothe first pilot sequence, and does not need to detect all possiblesecond pilot sequences, so that a quantity of detected pilots can besignificantly reduced, and pilot detection complexity is reduced. Thecorrespondence between the first pilot sequence and the second pilotsequence may be a one-to-multiple correspondence, a multiple-to-onecorrespondence, or a one-to-one correspondence.

Specifically, in a first aspect, in this embodiment of the presentinvention, one first pilot sequence may correspond to multiple secondpilot sequences, or one first pilot sequence may correspond to a groupof second pilot sequences. The group of second pilot sequences mayinclude two or more second pilot sequences. That is, the correspondencebetween the first pilot sequence and the second pilot sequence may be aone-to-multiple correspondence. Therefore, a quantity of first pilotsequences may be less than a quantity of second pilot sequences, so thatoverheads of the first pilot sequence can be reduced. However, it shouldbe understood that, in this case, compared with a case in which there isa one-to-one correspondence between the first pilot sequence and thesecond pilot sequence, accuracy of detecting the first pilot sequence bythe network device may be decreased, and at the same time, complexity ofdetecting the second pilot sequence by the network device may beincreased.

Further, the terminal device may first determine the first pilot number,and determine the first pilot sequence and the second pilot sequenceaccording to the first pilot number. One first pilot sequence maycorrespond to multiple second pilot sequences. For example, one pilotnumber may correspond to one first pilot sequence, and may correspond tomultiple second pilot sequences; or multiple pilot numbers mayrespectively correspond to multiple second pilot sequences but allcorrespond to one first pilot sequence, that is, different pilot numbersmay correspond to a same first pilot sequence but correspond todifferent second pilot sequences. Correspondingly, the network devicemay first detect the first pilot sequence on the first OFDM symbol. Whenthe network device detects the first pilot sequence, the network devicemay determine that the terminal device sending the first pilot sequenceis in an active state. Therefore, the network device may separatelydetect the multiple second pilot sequences corresponding to the firstpilot sequence. Because the network device needs to separately detectonly the multiple second pilot sequences corresponding to the firstpilot sequence, and does not need to detect all possible second pilotsequences, a quantity of detected pilots can be significantly reduced,and pilot detection complexity is reduced.

In a second aspect, in this embodiment of the present invention,multiple first pilot sequences may correspond to one second pilotsequence, or a group of first pilot sequences may correspond to onesecond pilot sequence. The group of first pilot sequences may includetwo or more first pilot sequences. That is, the correspondence betweenthe first pilot sequence and the second pilot sequence may be amultiple-to-one correspondence.

For example, the terminal device may first determine the first pilotnumber, and determine the first pilot sequence and the second pilotsequence according to the first pilot number. Multiple first pilotsequences may correspond to one second pilot sequence. For example, onepilot number may correspond to multiple first pilot sequences, and maycorrespond to one second pilot sequence; or multiple pilot numbers mayrespectively correspond to multiple first pilot sequences but allcorrespond to one second pilot sequence, that is, different pilotnumbers may correspond to different first pilot sequences but correspondto a same second pilot sequence. Correspondingly, the network device mayfirst detect the first pilot sequence on the first OFDM symbol. When thenetwork device detects the first pilot sequence, the network device maydetermine that the terminal device sending the first pilot sequence isin an active state. Therefore, the network device may detect the secondpilot sequence corresponding to the first pilot sequences. Because thenetwork device needs to detect only the second pilot sequencecorresponding to the first pilot sequences, and does not need to detectall possible second pilot sequences, a quantity of detected pilots canbe significantly reduced, and pilot detection complexity is reduced.

In a third aspect, in this embodiment of the present invention,preferably, the first pilot sequence is in one-to-one correspondencewith the second pilot sequence. For example, one pilot number mayuniquely correspond to one first pilot sequence, and may uniquelycorrespond to one second pilot sequence. It should be understood thatthis embodiment of the present invention is described merely by usingthis as an example, but the present invention is not limited thereto.For example, multiple pilot numbers may correspond to one first pilotsequence, and the first pilot sequence may uniquely correspond to onesecond pilot sequence; or multiple pilot numbers may correspond to onesecond pilot sequence, and the second pilot sequence may uniquelycorrespond to one first pilot sequence.

Specifically, for example, the terminal device may first determine thefirst pilot number, determine the first pilot sequence according to thefirst pilot number, and determine the second pilot sequence inone-to-one correspondence with the first pilot sequence. Further, theterminal device may respectively map the first pilot sequence and thesecond pilot sequence to the first OFDM symbol and the second OFDMsymbol of the grant free transmission resource, and send the first pilotsequence and the second pilot sequence by using the first OFDM symboland the second OFDM symbol. Correspondingly, the network device mayfirst detect the first pilot sequence on the first OFDM symbol. When thenetwork device detects the first pilot sequence, the network device maydetermine that the terminal device sending the first pilot sequence isin an active state. Therefore, the network device may detect one secondpilot sequence uniquely corresponding to the first pilot sequence, anddoes not need to detect all second pilot sequences, so that a quantityof detected pilots can be significantly reduced, and pilot detectioncomplexity is reduced.

In an uplink grant free transmission system, the terminal devicerandomly selects the second pilot sequence used for uplink datademodulation. Because different terminal devices may select a samesecond pilot sequence, a pilot collision may occur. In this case, thenetwork device considers that only one terminal device uses the secondpilot sequence, and consequently cannot perform correct decoding.Therefore, to reduce a pilot collision probability, sufficient secondpilot sequences are required for selection by a user.

However, in a current technology, uplink DMRSs are distinguished in asame OFDM symbol by using different cyclic shift values, and each OFDMsymbol can support a maximum of 12 orthogonal pilots. To satisfy asufficiently low pilot collision probability, hundreds or thousands ofpilots are required, so that a quantity of OFDM symbols for sendingDMRSs needs to be increased. However, simply increasing the quantity ofOFDM symbols for sending DMRSs can far from satisfying an actualrequirement. For example, one uplink subframe includes 14 OFDM symbolsin total, and even if all the OFDM symbols are used to send DMRSs, only14×12=168 pilots can be distinguished, and in this case, there are noother time-frequency resources used to send uplink data.

Therefore, in this embodiment of the present invention, to furtherreduce pilot overheads, multiple pilot sequences used for uplink datademodulation may be combined to form sufficient pilot sequences that canbe distinguished from each other, so that not only a sufficiently lowpilot collision probability can be satisfied, but pilot overheads canalso be significantly reduced.

Specifically, in this embodiment of the present invention, optionally,the second pilot sequence is a sub-sequence combination includingmultiple sub-sequences. That is, in this embodiment of the presentinvention, there may be a one-to-multiple correspondence, amultiple-to-one correspondence, or a one-to-one correspondence betweenthe first pilot sequence and the sub-sequence combination including twoor more sub-sequences. The sub-sequence is, for example, a DMRS.

For example, if each OFDM symbol can support a maximum of S orthogonalpilot sequences, and the pilot sequences supported by each OFDM symbolare used as one element in the sub-sequence combination, that is, pilotsequences carried on each OFDM symbol are used as one sub-sequence inthe sub-sequence combination, for D OFDM symbols, a maximum of S^(D)different sub-sequence combinations may be formed, so that a quantity ofavailable second pilot sequences in the system can be significantlyincreased. For example, according to parameter configuration of anexisting system, each OFDM symbol can support S=12 orthogonal pilotsequences, and two OFDM symbols can support a maximum of 12²=144different sub-sequence combinations, that is, 144 different second pilotsequences.

It should be understood that in an LTE system, it is assumed that eachOFDM symbol used to transmit a DMRS corresponds to K resource elementsREs, and for each OFDM symbol, different DMRSs may be distinguished byusing different cyclic shift values c_(i) of a base sequence b(k). Asshown in the following formula (6), each cyclic shift value c_(i)corresponds to one DMRS:r(k)=b(k)e ^((−jkc) ^(i) ⁾ ,k=1, . . . ,K  (6)

DMRSs corresponding to different cyclic shift values are orthogonal toeach other.

Therefore, in this embodiment of the present invention, optionally, thesecond pilot sequence is generated by using multiple cyclic shiftvalues. The multiple cyclic shift values are in one-to-onecorrespondence with the multiple sub-sequences. For example, in thisembodiment of the present invention, an i^(th) second pilot sequence maybe represented by a cyclic shift value combination (c_(i,1), . . . ,c_(i,d), . . . , c_(i,D)), where c_(i,d) corresponds to a cyclic shiftvalue of a sub-sequence on a d^(th) OFDM symbol, d is a natural number,and D≥d≥1.

It should be further understood that this embodiment of the presentinvention is described merely by using an example in which asub-sequence combination including multiple sub-sequences is used toincrease a quantity of second pilot sequences, but the present inventionis not limited thereto. For example, a method of increasing a quantityof pilot sequences supported by each second OFDM symbol may be used tosatisfy a requirement of a sufficiently low pilot collision probability.

Therefore, in this embodiment of the present invention, multiplesub-sequences are combined to form the second pilot sequence, so thatsufficient pilot sequences that may be distinguished from each other canbe formed, and not only the requirement of a sufficiently low pilotcollision probability can be satisfied, but pilot overheads can also besignificantly reduced.

Correspondingly, in S240, the terminal device maps the second pilotsequence to the second orthogonal frequency division multiplexing OFDMsymbol of the grant free transmission resource.

It should be understood that, in this embodiment of the presentinvention, the second OFDM symbol is an OFDM symbol used to transmit thesecond pilot sequence in the grant free transmission resource.Therefore, the second OFDM symbol may also be referred to as a secondpilot symbol. One grant free transmission resource may include one ormore second OFDM symbols. For example, in this embodiment of the presentinvention, the grant free transmission resource is, for example, a CTUaccess region. A second OFDM symbol in one CTU access region may includethree OFDM symbols. Further, the second OFDM symbol in the CTU accessregion may include the second OFDM symbol, the eighth OFDM symbol, andthe eleventh OFDM symbol of the CTU access region.

It should be further understood that, in this embodiment of the presentinvention, second OFDM symbols of grant free transmission resources mayinclude a same quantity of OFDM symbols or different quantities of OFDMsymbols. An OFDM symbol included in the first OFDM symbol may be thesame as or different from an OFDM symbol included in the second OFDMsymbol.

It should be further understood that this embodiment of the presentinvention is described merely by using this as an example, but thepresent invention is not limited thereto. For example, a second OFDMsymbol in one CTU access region may include only one OFDM symbol, or asecond OFDM symbol in one CTU access region may include two or more OFDMsymbols.

In this embodiment of the present invention, multiple sub-sequencesforming the sub-sequence combination may all be mapped to a same secondOFDM symbol of the grant free transmission resource, or may beseparately mapped to different second OFDM symbols of the grant freetransmission resource, or may be partially mapped to a same second OFDMsymbol of the grant free transmission resource. In the following,mapping of the second pilot sequence is described in detail withreference to FIG. 5A to FIG. 5F.

As shown in FIG. 5A to FIG. 5D, in this embodiment of the presentinvention, optionally, the mapping the second pilot sequence to a secondOFDM symbol of the grant free transmission resource includes:

mapping at least two of the multiple sub-sequences included in thesecond pilot sequence to a same second OFDM symbol of the grant freetransmission resource.

Specifically, in this embodiment of the present invention, at least twosub-sequences may be mapped to a same second OFDM symbol of the grantfree transmission resource. For example, in FIG. 5A, both a sub-sequence1 and a sub-sequence 2 are mapped to the fourth OFDM symbol of the grantfree transmission resource, and both the sub-sequence 1 and thesub-sequence 2 are mapped to an entire frequency band of the OFDMsymbol. For another example, in FIG. 5B and FIG. 5C, both a sub-sequence1 and a sub-sequence 2 are mapped to the fourth OFDM symbol of the grantfree transmission resource, and the sub-sequence 1 and the sub-sequence2 are mapped to different subbands of the OFDM symbol. In FIG. 5B, thesecond pilot sequence further includes a sub-sequence 3, thesub-sequence 3 is mapped to the eleventh OFDM symbol of the grant freetransmission resource, and the sub-sequence 3 is also mapped to a partof a frequency band of the OFDM symbol. In addition, in FIG. 5B and FIG.5C, for each sub-sequence, a part of a frequency band or subband towhich the sub-sequence is mapped is continuous. For another example, inFIG. 5D, a sub-sequence 1 and a sub-sequence 2 are mapped to differentsubbands of a same OFDM symbol. However, a part of a frequency band orsubband to which the sub-sequence 1 or the sub-sequence 2 is mapped isdiscontinuous.

In this embodiment of the present invention, at least two sub-sequencesmay be mapped to a same second OFDM symbol of the grant freetransmission resource. That is, all pilot sequences supported by an OFDMsymbol may be further divided into multiple groups, and one pilotsequence may be selected from each group as one sub-sequence in asub-sequence combination.

For example, it is assumed that for an uplink grant free transmissionsystem, each grant free transmission resource has two OFDM symbols usedto transmit the second pilot sequence, and the grant free transmissionresource is, for example, a CTU access region. That is, each CTU accessregion includes two second OFDM symbols, and each second OFDM symbol cansupport 12 orthogonal pilot sequences. The pilot sequence is, forexample, a DMRS. It is assumed that the second pilot sequence is asub-sequence combination (A, B, C) including three sub-sequences A, B,and C. The sub-sequence A may be one of six DMRSs supported by the firstsecond OFDM symbol, the sub-sequence B may be one of the other six DMRSssupported by the first second OFDM symbol, and the sub-sequence C may beone of 12 DMRSs supported by the second second OFDM symbol. That is, inthe three sub-sequences included in the second pilot sequence, thesub-sequence A and the sub-sequence B are mapped to a same second OFDMsymbol of the grant free transmission resource, and the sub-sequence Cis mapped to the other second OFDM symbol of the grant free transmissionresource. In this case, two second OFDM symbols included in each CTUaccess region can support a maximum of 6×6×12=432 different sub-sequencecombinations. That is, each CTU access region can support 432 differentsecond pilot sequences. Compared with the foregoing embodiment in whicheach CTU access region can support 144 different second pilot sequences,in this embodiment, each CTU access region can support more second pilotsequences, so that pilot overheads can be further reduced.

It should be understood that the foregoing embodiment is describedmerely by using an example in which two sub-sequences are mapped to asame second OFDM symbol of the grant free transmission resource, but thepresent invention is not limited thereto. When more sub-sequences aremapped to a same second OFDM symbol of the grant free transmissionresource, a same grant free transmission resource can support moresecond pilot sequences, and pilot overheads can be further significantlyreduced.

For example, it is assumed that the second pilot sequence is asub-sequence combination (A, B, D, C) including four sub-sequences A, B,C, and D. The sub-sequence A may be one of a first group of four DMRSssupported by the first second OFDM symbol, the sub-sequence B may be oneof a second group of four DMRSs supported by the first second OFDMsymbol, and the sub-sequence D may be one of a third group of four DMRSssupported by the first second OFDM symbol, but the sub-sequence C isstill one of 12 DMRSs supported by the second second OFDM symbol. Inthis case, two second OFDM symbols included in each CTU access regioncan support a maximum of 4×4×4×12=768 different second pilot sequences.

It should be understood that this embodiment of the present invention isdescribed merely by using an example in which DMRSs supported by onesecond OFDM symbol are grouped. When DMRSs supported by each second OFDMsymbol are grouped and therefore, the second pilot sequence includesmore sub-sequences, each CTU access region can support more differentsecond pilot sequences. For brevity, details are not described herein.

Further, in this embodiment of the present invention, optionally, asshown in FIG. 5A, the mapping the second pilot sequence to a second OFDMsymbol of the grant free transmission resource includes:

mapping all the multiple sub-sequences included in the second pilotsequence to a same second OFDM symbol of the grant free transmissionresource.

For example, in FIG. 5A, the second pilot sequence includes only asub-sequence 1 and a sub-sequence 2, and both the two sub-sequences aremapped to the fourth OFDM symbol of the grant free transmissionresource, so that the grant free transmission resource can support moresecond pilot sequences, and pilot overheads can be further reduced.

Further, in this embodiment of the present invention, optionally, asshown in FIG. 5B and FIG. 5C, the mapping the second pilot sequence to asecond OFDM symbol of the grant free transmission resource includes:

separately mapping at least two of the multiple sub-sequences includedin the second pilot sequence to different subbands of a same second OFDMsymbol of the grant free transmission resource.

For example, in FIG. 5B and FIG. 5C, a sub-sequence 1 and a sub-sequence2 included in the second pilot sequence are separately mapped todifferent subbands of the fourth OFDM symbol of the grant freetransmission resource, so that time-frequency resource overheads of thesystem can be reduced, and pilot overheads of the system can be furtherreduced.

It should be understood that sub-sequences mapped to different subbandsof the same second OFDM symbol may be the same or may be different.

Further, in this embodiment of the present invention, optionally, asshown in FIG. 5E and FIG. 5F, the mapping the second pilot sequence to asecond OFDM symbol of the grant free transmission resource includes:

separately mapping all the multiple sub-sequences included in the secondpilot sequence to different second OFDM symbols of the grant freetransmission resource.

For example, in FIG. 5E, the second pilot sequence includes asub-sequence 1 and a sub-sequence 2. The sub-sequence 1 is mapped to thefourth OFDM symbol of the grant free transmission resource and thesub-sequence 2 is mapped to the eleventh OFDM symbol of the grant freetransmission resource. In addition, the sub-sequence 1 is mapped to anentire frequency band of the fourth OFDM symbol and the sub-sequence 2is mapped to a part of a frequency band of the eleventh OFDM symbol. Foranother example, in FIG. 5F, a sub-sequence 1 is mapped to an entirefrequency band of the eighth OFDM symbol of the grant free transmissionresource and a sub-sequence 2 is mapped to an entire frequency band ofthe eleventh OFDM symbol of the grant free transmission resource.

Preferably, in this embodiment of the present invention, as shown inFIG. 5F, the mapping the second pilot sequence to a second OFDM symbolof the grant free transmission resource includes:

separately mapping all the multiple sub-sequences included in the secondpilot sequence to entire frequency bands of the different second OFDMsymbols of the grant free transmission resource, where the second OFDMsymbols are different from the first OFDM symbol.

Specifically, in FIG. 5F, the first pilot sequence is mapped to a partof a frequency band of the third OFDM symbol of the grant freetransmission resource. The second pilot sequence includes a sub-sequence1 and a sub-sequence 2. The sub-sequence 1 is mapped to an entirefrequency band of the eighth OFDM symbol of the grant free transmissionresource and the sub-sequence 2 is mapped to an entire frequency band ofthe eleventh OFDM symbol of the grant free transmission resource.

It should be understood that this embodiment of the present invention isdescribed merely by using schematic mapping diagrams shown in FIG. 5A toFIG. 5F as an example, but the present invention is not limited thereto.For brevity, details are not described herein.

In this embodiment of the present invention, for the second pilotsequence, reliability of transmitting the second pilot sequence may beimproved by using a diversity technology.

That is, in this embodiment of the present invention, optionally, themapping the second pilot sequence to a second OFDM symbol of the grantfree transmission resource includes:

repeatedly mapping the second pilot sequence to different second OFDMsymbols of the grant free transmission resource.

It should be understood that, in this embodiment of the presentinvention, detection reliability can be significantly improved by meansof time domain diversity or frequency domain diversity, but pilotoverheads are increased at the same time. In addition, in thisembodiment of the present invention, detection reliability may beimproved by means of spatial diversity. For example, a quantity ofreceive antennas of the base station may be increased, so that the basestation can separately detect signals received by using multiple receiveantennas, and therefore, detection reliability can be improved withoutincreasing pilot overheads. However, it should be understood that, inthis embodiment of the present invention, a quantity of transmitantennas of the terminal device may be increased. That is, the terminaldevice respectively sends different first pilot sequences on differentantennas. It may be considered that a corresponding terminal device isin an active state provided that the base station detects one of thefirst pilot sequences. In this manner, detection reliability can also beimproved, but pilot overheads need to be increased.

It should be further understood that, in this embodiment of the presentinvention, different second pilot sequences may be distinguished in atleast one of the following three manners: a time domain (an OFDMsymbol), a frequency domain (a subcarrier group or a subband), or a codedomain. For example, the second pilot sequences may be mapped todifferent OFDM symbols, to distinguish the second pilot sequences.Similarly, the second pilot sequences may be mapped to differentsubbands of an OFDM symbol, to distinguish the second pilot sequences.Further, if multiple second pilot sequences are mapped to a sametime-frequency resource, different second pilot sequences mapped to thesame time-frequency resource need to be orthogonal to each other. Inaddition, it should be further understood that, in this embodiment ofthe present invention, sub-sequences mapped to second OFDM symbols arenot completely the same, so that the network device can perform correctchannel estimation, to demodulate uplink data.

As described above, for example, in this embodiment of the presentinvention, the second pilot sequence may be represented by a cyclicshift value combination (c_(i,1), . . . , c_(i,d), . . . , c_(i,D)),where c_(i,d) corresponds to a cyclic shift value of a sub-sequence on ad^(th) OFDM symbol.

Description is provided still by using an example in which the firstpilot sequence and the second pilot sequence are determined by using thefirst pilot number i. It is assumed that the grant free transmissionresource is a CTU access region, a second OFDM symbol in one CTU accessregion may include two OFDM symbols, each OFDM symbol can support amaximum of 12 orthogonal DMRSs, each second pilot sequence is asub-sequence combination including two sub-sequences, and thesub-sequences are separately mapped to entire frequency bands ofdifferent second OFDM symbols of the grant free transmission resource.One CTU access region supports a maximum of 144 second pilot sequences(c_(i,1), c_(i,2)). Cyclic shift values c_(i,1) and c_(i,2) may bedetermined according to the following formulas: c_(i,1)=mod(i, 12), andc_(i,2)=└/12┘, where mod( ) is a modulo operator and └ ┘ is a roundingdown operator.

It should be understood that this embodiment of the present invention isdescribed merely by using the foregoing formulas as an example, but thepresent invention is not limited thereto. For example, the rounding downoperator in the foregoing formula may be transformed into a rounding upoperator.

In this embodiment of the present invention, if a quantity N of firstpilot sequences is equal to a quantity S^(D) of second pilot sequences,all possible sub-sequence combinations may be used. In this embodimentof the present invention, pilot overheads of the first pilot sequenceare in direct proportion to N, and pilot overheads of the second pilotsequence are in direct proportion to D. When D is relatively large, thepilot overheads of the first pilot sequence increase relatively fast,and N<S^(D) may occur. In this case, N sub-sequences in one-to-onecorrespondence with the first pilot sequence may be selected from S^(D)possible sub-sequence combinations. For example, when N=144, S=12, andD=3, a second pilot sequence (c_(i,1), c_(i,2), c_(i,3)) formed bycombining cyclic shift values c_(i,1), c_(i,2), and c_(i,3) may beconstructed, where c_(i,1)=mod(i, 12); c_(i,2)=└i/12┘;c_(i,3)=mod(c_(i,1)+c_(i,2), 12).

It should be pointed out that the foregoing design solution of thesecond pilot sequence is dedicated for a grant free transmission system,and there may be some collisions between different sub-sequences (DMRS).This design solution needs to be used together with the foregoingsolution of the first pilot sequence, and is not suitable to replace anexisting DMRS solution in a current system. A rule of using an ADRS anda DMRS together is described in the following by using an example. It isassumed that a DMRS occupies two OFDM symbols, 144 different DMRSs aresupported, and there is the following correspondence between a pilotnumber n and a cyclic shift value combination (c_(i,1), c_(i,2)):n=12c_(i,1)+c_(i,2). It may be verified that cyclic shift valuecombinations corresponding to two terminal devices whose pilot numbersare 1 and 2 are respectively (0, 1) and (0, 2). If pilots correspondingto the cyclic shift value combinations are separately detected whenstatuses of the terminal devices are unknown, an obtained result is nota correct channel estimation result. First, it is determined, by usingan ADRS, that the terminal devices whose pilot numbers are 1 and 2 areactive, and further it is determined, according to the correspondingcyclic shift value combinations, that the two terminal devices collideon the first OFDM symbol and can be distinguished on the second OFDMsymbol. Therefore, only a DMRS on the second OFDM symbol can be used forchannel estimation. There are a large quantity of potential users in agrant free system, but at the same time, there are a small quantity ofactive terminal devices. Therefore, a probability that multiple DMRSscompletely collide with each other is small, and this solution can bewell applied to the grant free system. Another advantage of thissolution is: Detection complexity of the ADRS is far lower than that ofthe DMRS. Because a user status is preliminarily determined by using theADRS in this solution, a quantity of times of DMRS detection is reduced,and entire detection complexity is thereby reduced.

It should be understood that, in this embodiment of the presentinvention, DMRSs may be mapped to multiple second OFDM symbols forsending. Different DMRSs may be mapped to a same pilot sequence on asame second OFDM symbol, but DMRSs mapped to different second OFDMsymbols are not completely the same.

In this embodiment of the present invention, it is assumed that for oneCTU access region, 144 different second pilot sequences are configuredin total, each second pilot sequence includes D sub-sequences,sub-sequences forming the second pilot sequence are, for example, DMRSs,that is, N_(DMRS)=144, and a quantity of subcarriers of each OFDM symbolis K. Each sub-sequence may be determined by using different cyclicshift values c_(i) of a base sequence b(k), as shown in the followingformula (6):r(k)=b(k)e ^((−jkc) ^(i) ⁾ ,k=1, . . . ,K  (6)

When D=3, a cyclic shift value c_(i,d) of each sub-sequence forming ani^(th) second pilot sequence may be, for example, determined accordingto the following formula (7):c _(i,1)=mod(i,12);c _(i,2) └i/12┘;c _(i,3)=mod(c _(i,1) +c_(i,2),12)  (7)

When D=2, a cyclic shift value c_(i,d) of each sub-sequence forming ani^(th) second pilot sequence may be, for example, determined accordingto the following formula (8):c _(i,1)=mod(i,k);c _(i,2) =└i/k┘;k=6,8, or 12  (8)

When D=3, a cyclic shift value c_(i,d) of each sub-sequence forming ani^(th) second pilot sequence may be, for example, determined accordingto the following formula (9) or (10):c _(i,1)=mod(i,k);c _(i,2) =└i/k┘;c _(i,3)=mod(c _(i,1) +c _(i,2),k);k=6,8, or 12  (9)c _(i,1)=mod(i,k);c _(i,2) =└i/k ² ┘;c _(i,3)=└ mod(i,k ²)/k┘; k=6,8, or12  (10)

When D=4, a cyclic shift value c_(i,d) of each sub-sequence forming ani^(th) second pilot sequence may be, for example, determined accordingto the following formula (11) or (12):c _(i,1)=mod(i,k);c _(i,2) =└i/k ² ┘;c _(i,3)=└ mod(i,k ²)/k┘;c_(i,4)=mod(c _(i,1) +c _(i,2) +c _(i,3) ,k); k=6,8, or 12  (11)c _(i,1)=mod(i,k);c _(i,2) =└i/k ³ ┘;c _(i,3)=└ mod(i,k ³)/k ² ┘;c_(i,4)=└ mod(i,k ²)/k┘;k=6,8, or 12  (12)

It should be understood that a cyclic shift value c_(i,d) of eachsub-sequence may be, for example, determined according to the foregoingformula, or may be determined according to a table.

For example, when D=2, a cyclic shift value c_(i,d) of each sub-sequenceforming an i^(th) second pilot sequence may be, for example, shown inTable 4. When D=3, a cyclic shift value c_(i,d) of each sub-sequenceforming an i^(th) second pilot sequence may be, for example, shown inTable 5.

TABLE 4 (D = 2) i Cyclic shift value (c_(i,1), c_(i,2)) 1 (0, 0) 2(0, 1) 3 (0, 2)

TABLE 5 (D = 3) i Cyclic shift value (c_(i,1), c_(i,2), c_(i,3)) 1 (0,0, 0) 2 (0, 1, 1) 3 (0, 2, 2)

It should be understood that this embodiment of the present invention isdescribed merely by using Table 4 and Table 5 as an example, but thepresent invention is not limited thereto. A cyclic shift value of eachsub-sequence of the second pilot sequence may be determined according toanother correspondence table, for example, a correspondence table of afirst pilot number and a cyclic shift value, or a correspondence tableof a first pilot sequence and a cyclic shift value.

In S250, the terminal device sends the first pilot sequence and thesecond pilot sequence by using the first OFDM symbol and the second OFDMsymbol.

It should be understood that, in this embodiment of the presentinvention, the terminal device may generate data according to apre-determined modulation and coding scheme, and send the first pilotsequence, the second pilot sequence, and the data on the grant freetransmission resource. It should be further understood that, in thisembodiment of the present invention, optionally, the terminal devicesends the first pilot sequence and the second pilot sequence to thenetwork device by using the first OFDM symbol and the second OFDMsymbol.

In this embodiment of the present invention, optionally, the determininga first pilot sequence used to indicate whether the terminal device isin an active state includes:

selecting the first pilot sequence from a first pilot sequence set.

In this embodiment of the present invention, optionally, the determininga second pilot sequence used for uplink data demodulation includes:

selecting the second pilot sequence from a second pilot sequence set.

In this embodiment of the present invention, optionally, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains, or another transmission resource in the foregoingdescription of the grant free transmission resource.

In this embodiment of the present invention, optionally, the method isapplied to device-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

In this embodiment of the present invention, optionally, the networkdevice is a base station and the terminal device is user equipment.

It should be understood that sequence numbers of the foregoing processesdo not mean execution sequences in various embodiments of the presentinvention. Execution sequences of the processes need to be determinedaccording to functions and internal logic of the processes, and shouldnot be construed as any limitation to implementation processes of theembodiments of the present invention.

Therefore, in the pilot sequence transmission method in this embodimentof the present invention, a terminal device determines a first pilotsequence used to indicate whether the terminal device is in an activestate and determines a second pilot sequence used for uplink datademodulation, respectively maps the first pilot sequence and the secondpilot sequence to a first OFDM symbol and a second OFDM symbol of agrant free transmission resource, and sends the first pilot sequence andthe second pilot sequence by using the first OFDM symbol and the secondOFDM symbol. Therefore, a network device can determine activeness of theterminal device by detecting the first pilot sequence, and can detectonly a second pilot sequence of a terminal device that is in an activestate, and does not need to detect all possible second pilot sequences,so that a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

In another aspect, in the pilot sequence transmission method in thisembodiment of the present invention, the second pilot sequence is set toa sub-sequence combination including multiple sub-sequences. For a samequantity of second OFDM symbols, a quantity of second pilot sequencessupported by the second OFDM symbols can be significantly increased.Therefore, a pilot collision probability can be significantly reduced,correctness of uplink data demodulation is increased, and a case inwhich excessive second OFDM symbols are occupied can be avoided, so thatpilot overheads can be significantly reduced, and more time-frequencyresources can be used for data transmission, that is, a datatransmission amount of a system can be significantly increased.

The pilot sequence transmission method in the embodiment of the presentinvention is described above from a perspective of a terminal devicewith reference to FIG. 1 to FIG. 5F. In the following, the pilotsequence transmission method in the embodiment of the present inventionis described from a perspective of a network device with reference toFIG. 6.

As shown in FIG. 6, a pilot sequence transmission method 300 accordingto an embodiment of the present invention, for example, may be performedby a network device in a grant free transmission system. The networkdevice is, for example, a base station. The method 300 includes thefollowing steps.

S310: Detect, on a first orthogonal frequency division multiplexing OFDMsymbol of a grant free transmission resource, a first pilot sequencesent by a terminal device, where the first pilot sequence is used toindicate whether the terminal device is in an active state.

S320: Detect, on a second OFDM symbol of the grant free transmissionresource, a second pilot sequence that is sent by the terminal deviceand that corresponds to the first pilot sequence, where the second pilotsequence is used for uplink data demodulation.

S330: Demodulate uplink data according to the second pilot sequence.

Specifically, in the grant free transmission system, there are a largequantity of terminal devices, but at the same time, there are anextremely small quantity of terminal devices that access a network, thatis, an extremely small quantity of terminal devices are in an activestate. Because the terminal device may randomly select a grant freetransmission resource to send data, a network device does not know inadvance which terminal devices are terminal devices that are in anactive state. Therefore, the network device needs to detect everypossible pilot, to determine a terminal device that is in an activestate. Complexity of this detection process is extremely high.

To reduce pilot detection complexity of the network device, in a grantfree access process of the terminal device, the terminal device mayselect the grant free transmission resource. For example, the terminaldevice may select a CTU access region. To transmit uplink data, theterminal device may determine the first pilot sequence and the secondpilot sequence. The first pilot sequence is used to indicate a status ofthe terminal device, for example, used to indicate whether the terminaldevice is in an active state. The second pilot sequence is used forchannel estimation, so as to be used for uplink data demodulation.Further, the terminal device may respectively map the first pilotsequence and the second pilot sequence to the first OFDM symbol and thesecond OFDM symbol of the grant free transmission resource, and send thefirst pilot sequence and the second pilot sequence by using the firstOFDM symbol and the second OFDM symbol.

Correspondingly, the network device may detect the first pilot sequenceon the first OFDM symbol of the grant free transmission resource. Whenthe network device detects the first pilot sequence, the network devicemay determine that the terminal device sending the first pilot sequenceis in an active state, so that the network device may detect, on thesecond OFDM symbol, only the second pilot sequence corresponding to thefirst pilot sequence. That is, the network device may detect only thesecond pilot sequence of the terminal device that is in an active state,perform channel estimation according to the second pilot sequence, andthereby demodulate uplink data, and the network device does not need todetect all possible second pilot sequences, so that a quantity ofdetected pilots can be significantly reduced, and pilot detectioncomplexity is reduced.

Therefore, in the pilot sequence transmission method in this embodimentof the present invention, a network device detects, on a first OFDMsymbol of a grant free transmission resource, a first pilot sequencesent by a terminal device, to determine, according to the first pilotsequence, whether the terminal device is in an active state; detects, ona second OFDM symbol of the grant free transmission resource, only asecond pilot sequence corresponding to the detected first pilotsequence, that is, detects only the second pilot sequence of theterminal device that is in an active state; and demodulates uplink dataaccording to the second pilot sequence. Therefore, the network devicedoes not need to detect all possible second pilot sequences, so that aquantity of detected pilots can be significantly reduced, and pilotdetection complexity is reduced.

It should be understood that, in this embodiment of the presentinvention, the first pilot sequence is used to indicate the status ofthe terminal device, for example, used to indicate whether the terminaldevice is in an active state. The first pilot sequence may be a Walshcode, or may be another pilot sequence used by the network device todetermine activeness or an active state of the terminal device. Forexample, the first pilot sequence is a Zadoff-Chu (ZC) sequence. Foranother example, the first pilot sequence is an activity detectionreference signal (ADRS), but this embodiment of the present invention isnot limited thereto.

It should be further understood that, in this embodiment of the presentinvention, the second pilot sequence is used for uplink datademodulation. Specifically, it may be understood that the second pilotsequence may be used by the network device for channel estimation, andthe network device further demodulates, according to a channelestimation result, uplink data sent by the terminal device. The secondpilot sequence is, for example, a DMRS. Certainly, the second pilotsequence may be another pilot sequence used by the network device foruplink data demodulation, and this embodiment of the present inventionis not limited thereto.

It should be further understood that, in this embodiment of the presentinvention, the grant free transmission resource may represent atime-frequency resource used to transmit uplink data in uplink grantfree transmission. For example, the grant free transmission resource isa CTU access region. It should be further understood that thisembodiment of the present invention is described merely by using a CTUaccess region as an example, but the present invention is not limitedthereto.

In this embodiment of the present invention, the network device maydetect the first pilot sequence on the first OFDM symbol of the grantfree transmission resource, to determine activeness of the terminaldevice, for example, determine whether the corresponding terminal deviceis in an active state. When the network device detects the first pilotsequence, the network device may determine that the terminal devicesending the first pilot sequence is in an active state, so that thenetwork device may determine a first pilot number of the terminal devicethat is in an active state, or determine a first pilot numbercorresponding to the first pilot sequence. Further, the network devicemay determine, according to the determined first pilot number, thesecond pilot sequence corresponding to the first pilot number, anddetect, on the second OFDM symbol, only the second pilot sequencecorresponding to the first pilot number. That is, the network device maydetect only the second pilot sequence of the terminal device that is inan active state, and may perform channel estimation according to thesecond pilot sequence, to demodulate uplink data according to a channelestimation result, and the network device does not need to detect allpossible second pilot sequences, so that a quantity of detected pilotscan be significantly reduced, and pilot detection complexity is reduced.

It should be understood that, in this embodiment of the presentinvention, the network device may determine, based on whether the firstpilot sequence is received or detected, whether the correspondingterminal device is in an active state. For example, the network devicemay determine, according to received signal strength, whether the firstpilot sequence is detected, to further determine whether thecorresponding terminal device is in an active state. For example, it isassumed that the first pilot sequence selected by the terminal device isWi, a corresponding channel is Hi, and a status variant Ii is set. Avalue of the status variant is 1 or 0 to indicate whether the terminaldevice is active. Then, a received signal Y may be represented as:Y=Σ _(i) IiHi·Wi, where

-   -   · represents a dot product of vectors. A correlation operation        is performed on the signal Y, to obtain a parameter Ai used to        determine whether the terminal device is active:        Ai=|Y ^(H) Wi| ²

If the parameter Ai is greater than a predetermined threshold T, thenetwork device may determine that the corresponding terminal device isin an active state, or if the parameter Ai is not greater than thepredetermined threshold T, the network device may determine that thecorresponding terminal device is in a non-active state, so that thenetwork device may determine, by detecting all first pilot sequences,the terminal device that is in an active state. Therefore, the networkdevice may detect only the second pilot sequence of the terminal devicethat is in an active state, so that a quantity of detected pilots can besignificantly reduced, and pilot detection complexity is reduced.

It should be understood that this embodiment of the present invention isdescribed merely by using the first pilot number as an example, but thepresent invention is not limited thereto. For example, the networkdevice may directly determine, according to a correspondence between thefirst pilot sequence and the second pilot sequence, a second pilotsequence that needs to be detected. The correspondence is described indetail in the following. For brevity, details are not described herein.

In this embodiment of the present invention, optionally, the detecting,on a first orthogonal frequency division multiplexing OFDM symbol of agrant free transmission resource, a first pilot sequence sent by aterminal device includes:

detecting the first pilot sequence in a part of a subband of the firstOFDM symbol of the grant free transmission resource.

Specifically, it should be understood that, in this embodiment of thepresent invention, the first OFDM symbol is an OFDM symbol used totransmit the first pilot sequence in the grant free transmissionresource. Therefore, the first OFDM symbol may also be referred to as afirst pilot symbol. One grant free transmission resource may include oneor more first OFDM symbols. For example, in this embodiment of thepresent invention, the grant free transmission resource is, for example,a CTU access region. A first OFDM symbol in one CTU access region mayinclude two OFDM symbols. Further, the first OFDM symbol in the CTUaccess region may include the third OFDM symbol and the tenth OFDMsymbol of the CTU access region. It should be further understood that,in this embodiment of the present invention, first OFDM symbols of grantfree transmission resources may include a same quantity of OFDM symbolsor different quantities of OFDM symbols.

It should be further understood that this embodiment of the presentinvention is described merely by using this as an example, but thepresent invention is not limited thereto. For example, a first OFDMsymbol in one CTU access region may include only one OFDM symbol, or afirst OFDM symbol in one CTU access region may include three or moreOFDM symbols.

For example, as shown in FIG. 4A, the terminal device may map the firstpilot sequence to a part of a subband of the third OFDM symbol, and thefirst pilot sequence does not occupy entire transmission bandwidth ofthe OFDM symbol, so that pilot overheads can be significantly reduced.Correspondingly, the network device needs to detect the first pilotsequence on the part of the subband of the third OFDM symbol of thegrant free transmission resource.

It should be understood that this embodiment of the present invention isdescribed merely by using an example in which the first pilot sequenceis mapped to four REs, but the present invention is not limited thereto.For example, the first pilot sequence may be mapped to two REs or eightREs. It should be further understood that this embodiment of the presentinvention is described merely by using an example in which the firstpilot sequence is mapped to a part of a subband of one OFDM symbol, butthe present invention is not limited thereto. For example, the firstpilot sequence may be mapped to parts of subbands of two or more OFDMsymbols.

In this embodiment of the present invention, optionally, an element ofthe first pilot sequence is a non-zero element. In this embodiment ofthe present invention, because the first pilot sequence is used toindicate activeness of the terminal device, the first pilot sequence maybe designed to have a relatively short length. Therefore, the non-zeroelement may be mapped to a part of a subband of the grant freetransmission resource. That is, the terminal device may send the firstpilot sequence on a part of a frequency resource of an OFDM symbol, anddoes not need to send the first pilot sequence over entire transmissionbandwidth of the OFDM symbol. Therefore, in one aspect, pilot overheadscan be significantly reduced, and in another aspect, a relatively shortfirst pilot sequence facilitates detection performed by the networkdevice, so that pilot detection complexity can be further reduced.

In another aspect, in this embodiment of the present invention,optionally, the first pilot sequence includes a first pilot sub-sequenceand a second pilot sub-sequence. Each element of the first pilotsub-sequence is a zero element, and an element of the second pilotsub-sequence is a non-zero element. The first pilot sequence may bemapped to a part of a subband of the grant free transmission resource,so that pilot overheads can be significantly reduced. Although comparedwith the first pilot sequence in the previous embodiment, the firstpilot sequence in this embodiment has a larger length, each element ofthe first pilot sub-sequence is a zero element, and the first pilotsequence may be mapped into a zero symbol on the grant free transmissionresource. Therefore, pilot detection complexity can also be reduced. Itshould be understood that, in this embodiment of the present invention,the first pilot sub-sequence including only a zero element is mappedinto a zero symbol, and the second pilot sub-sequence including anon-zero element is mapped into a non-zero symbol.

In this embodiment of the present invention, optionally, the detecting,on a first orthogonal frequency division multiplexing OFDM symbol of agrant free transmission resource, a first pilot sequence sent by aterminal device includes:

detecting the first pilot sequence in a first subband of the first OFDMsymbol of the grant free transmission resource, where the first subbandincludes M resource elements REs, a non-zero symbol formed after thenon-zero element is mapped is an M-order Walsh code, and M is a positiveinteger and is an exponential power of 2.

That is, the non-zero element included in the first pilot sequence ismapped to the M resource elements REs of the grant free transmissionresource, the non-zero symbol formed after the non-zero element ismapped is an M-order Walsh code, and M is a positive integer and is anexponential power of 2. Optionally, the M REs are M consecutive REs, sothat orthogonality between pilot sequences can be further enhanced.

It should be understood that this embodiment of the present invention isdescribed merely by using the Walsh code as an example, but the presentinvention is not limited thereto. For example, the first pilot sequencemay be a pseudo-noise sequence that is also referred to as a PNsequence, or the first pilot sequence may be a Zadoff-Chu (ZC) sequenceor an M sequence.

It should be further understood that, in this embodiment of the presentinvention, if the first pilot sequence is a Zadoff-Chu sequence,terminal devices mapped to a same subband may be distinguished by usingcyclic shift values and root numbers. If the first pilot sequence is anM sequence, terminal devices mapped to a same subband may bedistinguished by using cyclic shift values, that is, first pilotsequences of the terminal devices mapped to the same subband correspondto different cyclic shift values.

Optionally, in this embodiment of the present invention, the REsincluded in the first subband are M consecutive REs. That is, in thisembodiment of the present invention, the first pilot sequence ispreferably mapped to consecutive REs of a subband, so that betterorthogonality between different first pilot sequences is achieved, andpilot detection reliability of a system can be further improved.

In this embodiment of the present invention, the network device maydetermine the second pilot sequence according to a correspondencebetween the first pilot sequence and the second pilot sequence. Thecorrespondence may have multiple representation forms, for example, aformula or a table. That is, the network device may determine the secondpilot sequence by performing an operation according to a formula, or maydetermine, by means of table searching, the second pilot sequencecorresponding to the first pilot sequence. It should be understood thatthis embodiment of the present invention is described merely by usingthis as an example, but the present invention is not limited thereto.

In this embodiment of the present invention, optionally, when thecorrespondence between the first pilot sequence and the second pilotsequence is established by using the first pilot number, that thenetwork device detects, on a second OFDM symbol of the grant freetransmission resource, a second pilot sequence that is sent by theterminal device and that corresponds to the first pilot sequence mayinclude: determining, by the network device, the first pilot numberaccording to the detected first pilot sequence; determining, by thenetwork device, the second pilot sequence according to the first pilotnumber; and detecting, by the network device, the second pilot sequenceon the second OFDM symbol.

Specifically, in this embodiment of the present invention, the networkdevice may determine the first pilot number according to the detectedfirst pilot sequence. Further, the network device may determine thesecond pilot sequence according to a correspondence between the firstpilot number and the second pilot sequence. Therefore, the networkdevice may separately detect, on the second OFDM symbol, one or moresecond pilot sequences corresponding to one or more first pilotsequences. Optionally, the correspondence may have multiplerepresentation forms, for example, a formula or a table. That is, thenetwork device may determine the second pilot sequence by performing anoperation according to a formula, or may determine, by means of tablesearching, the second pilot sequence corresponding to the first pilotnumber. It should be understood that this embodiment of the presentinvention is described merely by using this as an example, but thepresent invention is not limited thereto. For example, in thisembodiment of the present invention, the network device may determinethe second pilot sequence corresponding to the first pilot number from asecond pilot sequence set.

In this embodiment of the present invention, the first pilot sequence isused to indicate a status of the terminal device, and the second pilotsequence is used for uplink data demodulation. There may be acorrespondence between the first pilot sequence and the second pilotsequence. Therefore, the network device may detect, by detecting thefirst pilot sequence, only the second pilot sequence corresponding tothe first pilot sequence, and does not need to detect all possiblesecond pilot sequences, so that a quantity of detected pilots can besignificantly reduced, and pilot detection complexity is reduced. Thecorrespondence between the first pilot sequence and the second pilotsequence may be a one-to-multiple correspondence, a multiple-to-onecorrespondence, or a one-to-one correspondence.

Specifically, in a first aspect, in this embodiment of the presentinvention, one first pilot sequence may correspond to multiple secondpilot sequences, or one first pilot sequence may correspond to a groupof second pilot sequences. The group of second pilot sequences mayinclude two or more second pilot sequences. That is, the correspondencebetween the first pilot sequence and the second pilot sequence may be aone-to-multiple correspondence. Therefore, a quantity of first pilotsequences may be less than a quantity of second pilot sequences, so thatoverheads of the first pilot sequence can be reduced. However, it shouldbe understood that, in this case, compared with a case in which there isa one-to-one correspondence between the first pilot sequence and thesecond pilot sequence, accuracy of detecting the first pilot sequence bythe network device may be decreased, and at the same time, complexity ofdetecting the second pilot sequence by the network device may beincreased.

Further, the terminal device may first determine the first pilot number,and determine the first pilot sequence and the second pilot sequenceaccording to the first pilot number. One first pilot sequence maycorrespond to multiple second pilot sequences. For example, one pilotnumber may correspond to one first pilot sequence, and may correspond tomultiple second pilot sequences; or multiple pilot numbers mayrespectively correspond to multiple second pilot sequences but allcorrespond to one first pilot sequence, that is, different pilot numbersmay correspond to a same first pilot sequence but correspond todifferent second pilot sequences. Correspondingly, the network devicemay first detect the first pilot sequence on the first OFDM symbol. Whenthe network device detects the first pilot sequence, the network devicemay determine that the terminal device sending the first pilot sequenceis in an active state. Therefore, the network device may separatelydetect the multiple second pilot sequences corresponding to the firstpilot sequence. Because the network device needs to separately detectonly the multiple second pilot sequences corresponding to the firstpilot sequence, and does not need to detect all possible second pilotsequences, a quantity of detected pilots can be significantly reduced,and pilot detection complexity is reduced.

In a second aspect, in this embodiment of the present invention,multiple first pilot sequences may correspond to one second pilotsequence, or a group of first pilot sequences may correspond to onesecond pilot sequence. The group of first pilot sequences may includetwo or more first pilot sequences. That is, the correspondence betweenthe first pilot sequence and the second pilot sequence may be amultiple-to-one correspondence.

For example, the terminal device may first determine the first pilotnumber, and determine the first pilot sequence and the second pilotsequence according to the first pilot number. Multiple first pilotsequences may correspond to one second pilot sequence. For example, onepilot number may correspond to multiple first pilot sequences, and maycorrespond to one second pilot sequence; or multiple pilot numbers mayrespectively correspond to multiple first pilot sequences but allcorrespond to one second pilot sequence, that is, a same pilot numbermay correspond to different first pilot sequences but correspond to asame second pilot sequence. Correspondingly, the network device mayfirst detect the first pilot sequence on the first OFDM symbol. When thenetwork device detects the first pilot sequence, the network device maydetermine that the terminal device sending the first pilot sequence isin an active state. Therefore, the network device may detect the secondpilot sequence corresponding to the first pilot sequences. Because thenetwork device needs to detect only the second pilot sequencecorresponding to the first pilot sequences, and does not need to detectall possible second pilot sequences, a quantity of detected pilots canbe significantly reduced, and pilot detection complexity is reduced.

In a third aspect, in this embodiment of the present invention,preferably, the first pilot sequence is in one-to-one correspondencewith the second pilot sequence. For example, one pilot number mayuniquely correspond to one first pilot sequence, and may uniquelycorrespond to one second pilot sequence. It should be understood thatthis embodiment of the present invention is described merely by usingthis as an example, but the present invention is not limited thereto.For example, multiple pilot numbers may correspond to one first pilotsequence, and the first pilot sequence may uniquely correspond to onesecond pilot sequence; or multiple pilot numbers may correspond to onesecond pilot sequence, and the second pilot sequence may uniquelycorrespond to one first pilot sequence.

In this embodiment of the present invention, optionally, the secondpilot sequence is a sub-sequence combination including multiplesub-sequences. That is, in this embodiment of the present invention,there may be a one-to-multiple correspondence, a multiple-to-onecorrespondence, or a one-to-one correspondence between the first pilotsequence and the sub-sequence combination including two or moresub-sequences. The sub-sequence is, for example, a DMRS.

For example, if each OFDM symbol can support a maximum of S orthogonalpilot sequences, and the pilot sequences supported by each OFDM symbolare used as one element in the sub-sequence combination, that is, pilotsequences carried on each OFDM symbol are used as one sub-sequence inthe sub-sequence combination, for D OFDM symbols, a maximum of S^(D)different sub-sequence combinations may be formed, so that a quantity ofavailable second pilot sequences in the system can be significantlyincreased. For example, according to parameter configuration of anexisting system, each OFDM symbol can support S=12 orthogonal pilotsequences, and two OFDM symbols can support a maximum of 12²=144different sub-sequence combinations, that is, 144 different second pilotsequences.

It should be further understood that this embodiment of the presentinvention is described merely by using an example in which asub-sequence combination including multiple sub-sequences is used toincrease a quantity of second pilot sequences, but the present inventionis not limited thereto. For example, a method of increasing a quantityof pilot sequences supported by each second OFDM symbol may be used tosatisfy a requirement of a sufficiently low pilot collision probability.

Therefore, in this embodiment of the present invention, multiplesub-sequences are combined to form the second pilot sequence, so thatsufficient pilot sequences that may be distinguished from each other canbe formed, and not only the requirement of a sufficiently low pilotcollision probability can be satisfied, but pilot overheads can also besignificantly reduced.

In this embodiment of the present invention, optionally, at least two ofthe multiple sub-sequences included in the second pilot sequence aresub-sequences mapped to a same second OFDM symbol of the grant freetransmission resource.

In this embodiment of the present invention, optionally, all themultiple sub-sequences included in the second pilot sequence aresub-sequences mapped to a same second OFDM symbol of the grant freetransmission resource.

In this embodiment of the present invention, optionally, at least two ofthe multiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to different subbands of a same secondOFDM symbol of the grant free transmission resource.

In this embodiment of the present invention, optionally, all themultiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to different second OFDM symbols of thegrant free transmission resource.

In this embodiment of the present invention, optionally, all themultiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to entire frequency bands of thedifferent second OFDM symbols of the grant free transmission resource,and the second OFDM symbols are different from the first OFDM symbol.

In this embodiment of the present invention, optionally, the secondpilot sequence is represented by multiple cyclic shift values, and themultiple cyclic shift values are in one-to-one correspondence with themultiple sub-sequences.

In this embodiment of the present invention, optionally, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains.

In this embodiment of the present invention, optionally, the method isapplied to device-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

In this embodiment of the present invention, optionally, the networkdevice is a base station and the terminal device is user equipment.

It should be understood that, in this embodiment of the presentinvention, detection reliability can be significantly improved by meansof time domain diversity or frequency domain diversity, but pilotoverheads are increased at the same time. In addition, in thisembodiment of the present invention, detection reliability may beimproved by means of spatial diversity. For example, a quantity ofreceive antennas of the base station may be increased, so that the basestation can separately detect signals received by using multiple receiveantennas, and therefore, detection reliability can be improved withoutincreasing pilot overheads. However, it should be understood that, inthis embodiment of the present invention, a quantity of transmitantennas of the terminal device may be increased. That is, the terminaldevice respectively sends different first pilot sequences on differentantennas. It may be considered that a corresponding terminal device isin an active state provided that the base station detects one of thefirst pilot sequences. In this manner, detection reliability can also beimproved, but pilot overheads need to be increased.

It should be further understood that, in this embodiment of the presentinvention, different second pilot sequences may be distinguished in atleast one of the following three manners: a time domain (an OFDMsymbol), a frequency domain (a subcarrier group or a subband), or a codedomain. For example, the second pilot sequences may be mapped todifferent OFDM symbols, to distinguish the second pilot sequences.Similarly, the second pilot sequences may be mapped to differentsubbands of an OFDM symbol, to distinguish the second pilot sequences.Further, if multiple second pilot sequences are mapped to a sametime-frequency resource, different second pilot sequences mapped to thesame time-frequency resource need to be orthogonal to each other. Inaddition, it should be further understood that, in this embodiment ofthe present invention, sub-sequences mapped to second OFDM symbols arenot completely the same, so that the network device can perform correctchannel estimation, to demodulate uplink data.

Therefore, in this embodiment of the present invention, optionally, thedetecting, on a first orthogonal frequency division multiplexing OFDMsymbol of a grant free transmission resource, a first pilot sequencesent by a terminal device includes: detecting, on different first OFDMsymbols of the grant free transmission resource, the first pilotsequence repeatedly mapped by the terminal device; and/or detecting, indifferent subbands of the first OFDM symbol of the grant freetransmission resource, the first pilot sequence repeatedly mapped by theterminal device.

Similarly, in this embodiment of the present invention, optionally, thedetecting, on a second OFDM symbol of the grant free transmissionresource, a second pilot sequence that is sent by the terminal deviceand that corresponds to the first pilot sequence includes: detecting, ondifferent second OFDM symbols of the grant free transmission resource,the second pilot sequence repeatedly mapped by the terminal device;and/or detecting, in different subbands of the second OFDM symbol of thegrant free transmission resource, the second pilot sequence repeatedlymapped by the terminal device.

It should be understood that sequence numbers of the foregoing processesdo not mean execution sequences in various embodiments of the presentinvention. Execution sequences of the processes need to be determinedaccording to functions and internal logic of the processes, and shouldnot be construed as any limitation to implementation processes of theembodiments of the present invention.

Therefore, in the pilot sequence transmission method in this embodimentof the present invention, a network device detects, on a first OFDMsymbol of a grant free transmission resource, a first pilot sequencesent by a terminal device, to determine, according to the first pilotsequence, whether the terminal device is in an active state; detects, ona second OFDM symbol of the grant free transmission resource, only asecond pilot sequence corresponding to the detected first pilotsequence, that is, detects only the second pilot sequence of theterminal device that is in an active state; and demodulates uplink dataaccording to the second pilot sequence. Therefore, the network devicedoes not need to detect all possible second pilot sequences, so that aquantity of detected pilots can be significantly reduced, and pilotdetection complexity is reduced.

In another aspect, in the pilot sequence transmission method in thisembodiment of the present invention, the second pilot sequence is set toa sub-sequence combination including multiple sub-sequences. For a samequantity of second OFDM symbols, a quantity of second pilot sequencessupported by the second OFDM symbol can be significantly increased.Therefore, a pilot collision probability can be significantly reduced,correctness of uplink data demodulation is increased, and a case inwhich excessive second OFDM symbols are occupied can be avoided, so thatpilot overheads can be significantly reduced, and more time-frequencyresources can be used for data transmission, that is, a datatransmission amount of a system can be significantly increased.

The pilot sequence transmission method according to the embodiments ofthe present invention is described above in detail with reference toFIG. 1 to FIG. 6, and in the following, a pilot sequence transmissionapparatus according to an embodiment of the present invention isdescribed in detail with reference to FIG. 7 to FIG. 11.

FIG. 7 shows a pilot sequence transmission apparatus 500 according to anembodiment of the present invention. As shown in FIG. 7, the apparatus500 includes:

a first determining module 510, configured to determine a first pilotsequence used to indicate whether a terminal device is in an activestate;

a second determining module 520, configured to determine a second pilotsequence used for uplink data demodulation;

a first mapping module 530, configured to map the first pilot sequencedetermined by the first determining module 510 to a first orthogonalfrequency division multiplexing OFDM symbol of a grant free transmissionresource;

a second mapping module 540, configured to map the second pilot sequencedetermined by the second determining module 520 to a second OFDM symbolof the grant free transmission resource; and

a sending module 550, configured to send the first pilot sequence andthe second pilot sequence by using the first OFDM symbol mapped by thefirst mapping module 530 and the second OFDM symbol mapped by the secondmapping module 540.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a terminal device determines afirst pilot sequence used to indicate whether the terminal device is inan active state and determines a second pilot sequence used for uplinkdata demodulation, respectively maps the first pilot sequence and thesecond pilot sequence to a first OFDM symbol and a second OFDM symbol ofa grant free transmission resource, and sends the first pilot sequenceand the second pilot sequence by using the first OFDM symbol and thesecond OFDM symbol. Therefore, a network device can determine activenessof the terminal device by detecting the first pilot sequence, and candetect only a second pilot sequence of a terminal device that is in anactive state, and does not need to detect all possible second pilotsequences, so that a quantity of detected pilots can be significantlyreduced, and pilot detection complexity is reduced.

In this embodiment of the present invention, as shown in FIG. 8,optionally, the apparatus 500 further includes a third determiningmodule 560, configured to determine a first pilot number.

The first determining module 510 is specifically configured to determinethe first pilot sequence according to the first pilot number; and

the second determining module 520 is specifically configured todetermine the second pilot sequence according to the first pilot number.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a terminal device determines afirst pilot number, determines a first pilot sequence and a second pilotsequence according to the first pilot number, respectively maps thefirst pilot sequence and the second pilot sequence to a first OFDMsymbol and a second OFDM symbol of a grant free transmission resource,and sends the first pilot sequence and the second pilot sequence byusing the first OFDM symbol and the second OFDM symbol. Therefore, anetwork device can determine activeness of the terminal device bydetecting the first pilot sequence, and can detect only the second pilotsequence corresponding to the first pilot sequence, and does not need todetect all possible second pilot sequences, so that a quantity ofdetected pilots can be significantly reduced, and pilot detectioncomplexity is reduced.

In this embodiment of the present invention, optionally, the thirddetermining module 560 is specifically configured to:

determine the first pilot number according to an identifier of theterminal device; or

determine the first pilot number according to an identifier of the grantfree transmission resource and an identifier of the terminal device; or

generate the first pilot number by using a random number generator.

In this embodiment of the present invention, optionally, the firstmapping module 530 is specifically configured to map the first pilotsequence to a part of a subband of the first OFDM symbol of the grantfree transmission resource.

In this embodiment of the present invention, optionally, an element ofthe first pilot sequence is a non-zero element.

In this embodiment of the present invention, optionally, the first pilotsequence includes a first pilot sub-sequence and a second pilotsub-sequence. Each element of the first pilot sub-sequence is a zeroelement, and an element of the second pilot sub-sequence is a non-zeroelement.

In this embodiment of the present invention, optionally, the firstmapping module 530 is specifically configured to map the non-zeroelement included in the first pilot sequence to a first subband of thefirst OFDM symbol of the grant free transmission resource. The firstsubband includes M resource elements REs, a non-zero symbol formed afterthe non-zero element is mapped is an M-order Walsh code, and M is apositive integer and is an exponential power of 2.

In this embodiment of the present invention, optionally, the REsincluded in the first subband are M consecutive REs.

In this embodiment of the present invention, optionally, the firstmapping module 530 is specifically configured to:

repeatedly map the first pilot sequence to different first OFDM symbolsof the grant free transmission resource; and/or

repeatedly map the first pilot sequence to different subbands of thefirst OFDM symbol of the grant free transmission resource.

In this embodiment of the present invention, optionally, the first pilotsequence is in one-to-one correspondence with the second pilot sequence.

In this embodiment of the present invention, optionally, the secondpilot sequence is a sub-sequence combination including multiplesub-sequences.

In this embodiment of the present invention, optionally, the secondmapping module 540 is specifically configured to map at least two of themultiple sub-sequences included in the second pilot sequence to a samesecond OFDM symbol of the grant free transmission resource.

In this embodiment of the present invention, optionally, the secondmapping module 540 is specifically configured to map all the multiplesub-sequences included in the second pilot sequence to a same secondOFDM symbol of the grant free transmission resource.

In this embodiment of the present invention, optionally, the secondmapping module 540 is specifically configured to separately map at leasttwo of the multiple sub-sequences included in the second pilot sequenceto different subbands of a same second OFDM symbol of the grant freetransmission resource.

In this embodiment of the present invention, optionally, the secondmapping module 540 is specifically configured to separately map all themultiple sub-sequences included in the second pilot sequence todifferent second OFDM symbols of the grant free transmission resource.

In this embodiment of the present invention, optionally, the secondmapping module 540 is specifically configured to separately map all themultiple sub-sequences included in the second pilot sequence to entirefrequency bands of the different second OFDM symbols of the grant freetransmission resource. The second OFDM symbols are different from thefirst OFDM symbol.

In this embodiment of the present invention, optionally, the secondpilot sequence is generated by using multiple cyclic shift values, andthe multiple cyclic shift values are in one-to-one correspondence withthe multiple sub-sequences.

In this embodiment of the present invention, optionally, the secondmapping module 540 is specifically configured to repeatedly map thesecond pilot sequence to different second OFDM symbols of the grant freetransmission resource.

In this embodiment of the present invention, optionally, the firstdetermining module 510 is specifically configured to select the firstpilot sequence from a first pilot sequence set.

In this embodiment of the present invention, optionally, the seconddetermining module 520 is specifically configured to select the secondpilot sequence from a second pilot sequence set.

In this embodiment of the present invention, optionally, the sendingmodule 550 is configured to send the first pilot sequence and the secondpilot sequence to a network device by using the first OFDM symbol mappedby the first mapping module 530 and the second OFDM symbol mapped by thesecond mapping module 540.

In this embodiment of the present invention, optionally, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains.

In this embodiment of the present invention, optionally, the apparatusis applied to device-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

In this embodiment of the present invention, optionally, the networkdevice is a base station, and the terminal device is user equipment.

In this embodiment of the present invention, optionally, the apparatus500 is a terminal device.

It should be understood that the apparatus 500 in this embodiment of thepresent invention may correspond to the terminal device in the methodembodiment of the present invention, and the foregoing and otheroperations and/or functions of the modules in the apparatus 500 areseparately used to implement corresponding procedures of the method 200shown in FIG. 1 to FIG. 5F. For brevity, descriptions of the methodembodiment may be applicable to the apparatus embodiment, and detailsare not described herein again.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a terminal device determines afirst pilot sequence used to indicate whether the terminal device is inan active state and determines a second pilot sequence used for uplinkdata demodulation, respectively maps the first pilot sequence and thesecond pilot sequence to a first OFDM symbol and a second OFDM symbol ofa grant free transmission resource, and sends the first pilot sequenceand the second pilot sequence by using the first OFDM symbol and thesecond OFDM symbol. Therefore, a network device can determine activenessof the terminal device by detecting the first pilot sequence, and candetect only a second pilot sequence of a terminal device that is in anactive state, and does not need to detect all possible second pilotsequences, so that a quantity of detected pilots can be significantlyreduced, and pilot detection complexity is reduced.

In another aspect, in the pilot sequence transmission apparatus in thisembodiment of the present invention, the second pilot sequence is set toa sub-sequence combination including multiple sub-sequences. For a samequantity of second OFDM symbols, a quantity of second pilot sequencessupported by the second OFDM symbols can be significantly increased.Therefore, a pilot collision probability can be significantly reduced,correctness of uplink data demodulation is increased, and a case inwhich excessive second OFDM symbols are occupied can be avoided, so thatpilot overheads can be significantly reduced, and more time-frequencyresources can be used for data transmission, that is, a datatransmission amount of a system can be significantly increased.

FIG. 9 shows a pilot sequence transmission apparatus 600 according toanother embodiment of the present invention. As shown in FIG. 9, theapparatus 600 includes:

a first detection module 610, configured to detect, on a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource, a first pilot sequence sent by a terminal device,where the first pilot sequence is used to indicate whether the terminaldevice is in an active state;

a second detection module 620, configured to detect, on a second OFDMsymbol of the grant free transmission resource, a second pilot sequencethat is sent by the terminal device and that corresponds to the firstpilot sequence detected by the first detection module 610, where thesecond pilot sequence is used for uplink data demodulation; and

a processing module 630, configured to demodulate uplink data accordingto the second pilot sequence detected by the second detection module620.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a network device detects, on afirst OFDM symbol of a grant free transmission resource, a first pilotsequence sent by a terminal device, to determine, according to the firstpilot sequence, whether the terminal device is in an active state;detects, on a second OFDM symbol of the grant free transmissionresource, only a second pilot sequence corresponding to the detectedfirst pilot sequence, that is, detects only the second pilot sequence ofthe terminal device that is in an active state; and demodulates uplinkdata according to the second pilot sequence. Therefore, the networkdevice does not need to detect all possible second pilot sequences, sothat a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

In this embodiment of the present invention, optionally, the firstdetection module 610 is specifically configured to detect the firstpilot sequence in a part of a subband of the first OFDM symbol of thegrant free transmission resource.

In this embodiment of the present invention, optionally, an element ofthe first pilot sequence is a non-zero element.

In this embodiment of the present invention, optionally, the first pilotsequence includes a first pilot sub-sequence and a second pilotsub-sequence. Each element of the first pilot sub-sequence is a zeroelement, and an element of the second pilot sub-sequence is a non-zeroelement.

In this embodiment of the present invention, optionally, the firstdetection module 610 is specifically configured to detect the firstpilot sequence in a first subband of the first OFDM symbol of the grantfree transmission resource. The first subband includes M resourceelements REs, a non-zero symbol formed after the non-zero element ismapped is an M-order Walsh code, and M is a positive integer and is anexponential power of 2.

In this embodiment of the present invention, optionally, the REsincluded in the first subband are M consecutive REs.

In this embodiment of the present invention, optionally, the first pilotsequence is in one-to-one correspondence with the second pilot sequence.

In this embodiment of the present invention, optionally, the secondpilot sequence is a sub-sequence combination including multiplesub-sequences.

In this embodiment of the present invention, optionally, at least two ofthe multiple sub-sequences included in the second pilot sequence aresub-sequences mapped to a same second OFDM symbol of the grant freetransmission resource.

In this embodiment of the present invention, optionally, all themultiple sub-sequences included in the second pilot sequence aresub-sequences mapped to a same second OFDM symbol of the grant freetransmission resource.

In this embodiment of the present invention, optionally, at least two ofthe multiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to different subbands of a same secondOFDM symbol of the grant free transmission resource.

In this embodiment of the present invention, optionally, all themultiple sub-sequences included in the second pilot sequence aresub-sequences separately mapped to different second OFDM symbols of thegrant free transmission resource.

In this embodiment of the present invention, optionally, the secondpilot sequence is represented by multiple cyclic shift values, and themultiple cyclic shift values are in one-to-one correspondence with themultiple sub-sequences.

In this embodiment of the present invention, optionally, the grant freetransmission resource is a transmission resource combining time andfrequency, or a transmission resource combining time, frequency, andcode domains.

In this embodiment of the present invention, optionally, the apparatusis applied to device-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

In this embodiment of the present invention, optionally, the networkdevice is a base station and the terminal device is user equipment.

In this embodiment of the present invention, optionally, the apparatus600 is a network device.

It should be understood that the apparatus 600 in this embodiment of thepresent invention may correspond to the network device in the methodembodiment of the present invention, and the foregoing and otheroperations and/or functions of the modules in the apparatus 600 areseparately used to implement corresponding procedures of the method 300shown in FIG. 6. For brevity, descriptions of the method embodiment maybe applicable to the apparatus embodiment, and details are not describedherein again.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a network device detects, on afirst OFDM symbol of a grant free transmission resource, a first pilotsequence sent by a terminal device, to determine, according to the firstpilot sequence, whether the terminal device is in an active state;detects, on a second OFDM symbol of the grant free transmissionresource, only a second pilot sequence corresponding to the detectedfirst pilot sequence, that is, detects only the second pilot sequence ofthe terminal device that is in an active state; and demodulates uplinkdata according to the second pilot sequence. Therefore, the networkdevice does not need to detect all possible second pilot sequences, sothat a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

In another aspect, in the pilot sequence transmission apparatus in thisembodiment of the present invention, the second pilot sequence is set toa sub-sequence combination including multiple sub-sequences. For a samequantity of second OFDM symbols, a quantity of second pilot sequencessupported by the second OFDM symbols can be significantly increased.Therefore, a pilot collision probability can be significantly reduced,correctness of uplink data demodulation is increased, and a case inwhich excessive second OFDM symbols are occupied can be avoided, so thatpilot overheads can be significantly reduced, and more time-frequencyresources can be used for data transmission, that is, a datatransmission amount of a system can be significantly increased.

As shown in FIG. 10, an embodiment of the present invention furtherprovides a pilot sequence transmission apparatus 800. The apparatus 800includes a processor 810 and a transmitter 840. The processor 810 isconnected to the transmitter 840. Optionally, the apparatus 800 furtherincludes a memory 820. The memory 820 is separately connected to theprocessor 810 and the transmitter 840. Further optionally, the apparatus800 includes a bus system 830. The processor 810, the memory 820, andthe transmitter 840 may be connected by using the bus system 830. Thememory 820 may be configured to store an instruction. The processor 810is configured to execute the instruction stored in the memory 820, tocontrol the transmitter 840 to send a signal. The processor 810 isconfigured to:

determine a first pilot sequence used to indicate whether a terminaldevice is in an active state;

determine a second pilot sequence used for uplink data demodulation;

map the first pilot sequence to a first orthogonal frequency divisionmultiplexing OFDM symbol of a grant free transmission resource; and

map the second pilot sequence to a second OFDM symbol of the grant freetransmission resource.

The transmitter 840 is configured to:

send the first pilot sequence and the second pilot sequence by using thefirst OFDM symbol and the second OFDM symbol.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a terminal device determines afirst pilot sequence used to indicate whether the terminal device is inan active state and determines a second pilot sequence used for uplinkdata demodulation, respectively maps the first pilot sequence and thesecond pilot sequence to a first OFDM symbol and a second OFDM symbol ofa grant free transmission resource, and sends the first pilot sequenceand the second pilot sequence by using the first OFDM symbol and thesecond OFDM symbol. Therefore, a network device can determine activenessof the terminal device by detecting the first pilot sequence, and candetect only a second pilot sequence of a terminal device that is in anactive state, and does not need to detect all possible second pilotsequences, so that a quantity of detected pilots can be significantlyreduced, and pilot detection complexity is reduced.

It should be understood that, in this embodiment of the presentinvention, the processor 810 may be a central processing unit (CPU), orthe processor 810 may be another general purpose processor, a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a field programmable gate array (FPGA) or another programmablelogic device, a discrete gate or a transistor logic device, a discretehardware component, or the like. The general purpose processor may be amicroprocessor or the processor may be any conventional processor or thelike.

The memory 820 may include a read-only memory and a random accessmemory, and provides an instruction and data to the processor 810. Apart of the memory 820 may further include a non-volatile random accessmemory. For example, the memory 820 may further store device typeinformation.

The bus system 830 may further include a power bus, a control bus, astatus signal bus, and the like in addition to a data bus. However, forclear description, various types of buses in the figure are marked asthe bus system 830.

In an implementation process, the steps of the foregoing method may becompleted by using an integrated logic circuit of hardware in theprocessor 810 or an instruction in a form of software. Steps of themethod disclosed with reference to the embodiments of the presentinvention may be directly performed and completed by a hardwareprocessor, or may be performed and completed by a combination ofhardware and software modules in the processor. The software module maybe located in a mature storage medium in the art, such as a randomaccess memory, a flash memory, a read-only memory, a programmableread-only memory, an electrically-erasable programmable memory, or aregister. The storage medium is located in the memory 820, and theprocessor 810 reads information in the memory 820 and completes thesteps of the foregoing method in combination with hardware of theprocessor 810. To avoid repetition, details are not described hereinagain.

Optionally, in an embodiment, the processor 810 is further configured todetermine a first pilot number.

That the processor 810 determines a first pilot sequence used toindicate whether a terminal device is in an active state includes:

determining the first pilot sequence according to the first pilotnumber.

The determining a second pilot sequence used for uplink datademodulation includes: determining the second pilot sequence accordingto the first pilot number.

Optionally, in an embodiment, that the processor 810 determines a firstpilot number includes:

determining the first pilot number according to an identifier of theterminal device; or

determining the first pilot number according to an identifier of thegrant free transmission resource and an identifier of the terminaldevice; or generating the first pilot number by using a random numbergenerator.

Optionally, in an embodiment, that the processor 810 maps the firstpilot sequence to a first orthogonal frequency division multiplexingOFDM symbol of a grant free transmission resource includes:

mapping the first pilot sequence to a part of a subband of the firstOFDM symbol of the grant free transmission resource.

Optionally, in an embodiment, an element of the first pilot sequence isa non-zero element.

Optionally, in an embodiment, the first pilot sequence includes a firstpilot sub-sequence and a second pilot sub-sequence. Each element of thefirst pilot sub-sequence is a zero element, and an element of the secondpilot sub-sequence is a non-zero element.

Optionally, in an embodiment, that the processor 810 maps the firstpilot sequence to a first orthogonal frequency division multiplexingOFDM symbol of a grant free transmission resource includes:

mapping the non-zero element included in the first pilot sequence to afirst subband of the first OFDM symbol of the grant free transmissionresource, where the first subband includes M resource elements REs, anon-zero symbol formed after the non-zero element is mapped is anM-order Walsh code, and M is a positive integer and is an exponentialpower of 2.

Optionally, in an embodiment, the REs included in the first subband areM consecutive REs.

Optionally, in an embodiment, that the processor 810 maps the firstpilot sequence to a first orthogonal frequency division multiplexingOFDM symbol of a grant free transmission resource includes:

repeatedly mapping the first pilot sequence to different first OFDMsymbols of the grant free transmission resource; and/or

repeatedly mapping the first pilot sequence to different subbands of thefirst OFDM symbol of the grant free transmission resource.

Optionally, in an embodiment, the first pilot sequence is in one-to-onecorrespondence with the second pilot sequence.

Optionally, in an embodiment, the second pilot sequence is asub-sequence combination including multiple sub-sequences.

Optionally, in an embodiment, that the processor 810 maps the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes:

mapping at least two of the multiple sub-sequences included in thesecond pilot sequence to a same second OFDM symbol of the grant freetransmission resource.

Optionally, in an embodiment, that the processor 810 maps the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes:

mapping all the multiple sub-sequences included in the second pilotsequence to a same second OFDM symbol of the grant free transmissionresource.

Optionally, in an embodiment, that the processor 810 maps the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes:

separately mapping at least two of the multiple sub-sequences includedin the second pilot sequence to different subbands of a same second OFDMsymbol of the grant free transmission resource.

Optionally, in an embodiment, that the processor 810 maps the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes:

separately mapping all the multiple sub-sequences included in the secondpilot sequence to different second OFDM symbols of the grant freetransmission resource.

Optionally, in an embodiment, that the processor 810 maps the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes:

separately mapping all the multiple sub-sequences included in the secondpilot sequence to entire frequency bands of the different second OFDMsymbols of the grant free transmission resource, where the second OFDMsymbols are different from the first OFDM symbol.

Optionally, in an embodiment, the second pilot sequence is generated byusing multiple cyclic shift values, and the multiple cyclic shift valuesare in one-to-one correspondence with the multiple sub-sequences.

Optionally, in an embodiment, that the processor 810 maps the secondpilot sequence to a second OFDM symbol of the grant free transmissionresource includes:

repeatedly mapping the second pilot sequence to different second OFDMsymbols of the grant free transmission resource.

Optionally, in an embodiment, the processor 810 is specificallyconfigured to select the first pilot sequence from a first pilotsequence set.

Optionally, in an embodiment, the processor 810 is specificallyconfigured to select the second pilot sequence from a second pilotsequence set.

Optionally, in an embodiment, the grant free transmission resource is atransmission resource combining time and frequency, or a transmissionresource combining time, frequency, and code domains.

Optionally, in an embodiment, the apparatus is applied todevice-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

Optionally, in an embodiment, the network device is a base station, andthe terminal device is user equipment.

It should be understood that the pilot sequence transmission apparatus800 in this embodiment of the present invention may correspond to theterminal device and the apparatus 500 in the embodiments of the presentinvention, and may correspond to an execution body of the method in theembodiments of the present invention. In addition, the foregoing andother operations and/or functions of the modules in the apparatus 800are used to implement corresponding procedures of the method in FIG. 1to FIG. 5F. For brevity, descriptions of the method embodiment may beapplicable to the apparatus embodiment, and details are not describedherein again.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a terminal device determines afirst pilot sequence used to indicate whether the terminal device is inan active state and determines a second pilot sequence used for uplinkdata demodulation, respectively maps the first pilot sequence and thesecond pilot sequence to a first OFDM symbol and a second OFDM symbol ofa grant free transmission resource, and sends the first pilot sequenceand the second pilot sequence by using the first OFDM symbol and thesecond OFDM symbol. Therefore, a network device can determine activenessof the terminal device by detecting the first pilot sequence, and candetect only a second pilot sequence of a terminal device that is in anactive state, and does not need to detect all possible second pilotsequences, so that a quantity of detected pilots can be significantlyreduced, and pilot detection complexity is reduced.

In another aspect, in the pilot sequence transmission apparatus in thisembodiment of the present invention, the second pilot sequence is set toa sub-sequence combination including multiple sub-sequences. For a samequantity of second OFDM symbols, a quantity of second pilot sequencessupported by the second OFDM symbols can be significantly increased.Therefore, a pilot collision probability can be significantly reduced,correctness of uplink data demodulation is increased, and a case inwhich excessive second OFDM symbols are occupied can be avoided, so thatpilot overheads can be significantly reduced, and more time-frequencyresources can be used for data transmission, that is, a datatransmission amount of a system can be significantly increased.

As shown in FIG. 11, an embodiment of the present invention furtherprovides a pilot sequence transmission apparatus 900. The apparatus 900includes a processor 910. Optionally, the apparatus 900 includes amemory 920. The processor 910 is connected to the memory 920. Furtheroptionally, the apparatus 900 includes a bus system 930. The processor910 and the memory 920 may be connected by using the bus system 930, thememory 920 is configured to store an instruction, and the processor 910is configured to execute the instruction stored in the memory 920.

The processor 910 is configured to:

detect, on a first orthogonal frequency division multiplexing OFDMsymbol of a grant free transmission resource, a first pilot sequencesent by a terminal device, where the first pilot sequence is used toindicate whether the terminal device is in an active state;

detect, on a second OFDM symbol of the grant free transmission resource,a second pilot sequence that is sent by the terminal device and thatcorresponds to the first pilot sequence, where the second pilot sequenceis used for uplink data demodulation; and

demodulate uplink data according to the second pilot sequence.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a network device detects, on afirst OFDM symbol of a grant free transmission resource, a first pilotsequence sent by a terminal device, to determine, according to the firstpilot sequence, whether the terminal device is in an active state;detects, on a second OFDM symbol of the grant free transmissionresource, only a second pilot sequence corresponding to the detectedfirst pilot sequence, that is, detects only the second pilot sequence ofthe terminal device that is in an active state; and demodulates uplinkdata according to the second pilot sequence. Therefore, the networkdevice does not need to detect all possible second pilot sequences, sothat a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

It should be understood that, in this embodiment of the presentinvention, the processor 910 may be a central processing unit (CPU), orthe processor 910 may be another general purpose processor, a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a field programmable gate array (FPGA) or another programmablelogic device, a discrete gate or a transistor logic device, a discretehardware component, or the like. The general purpose processor may be amicroprocessor or the processor may be any conventional processor or thelike.

The memory 920 may include a read-only memory and a random accessmemory, and provides an instruction and data to the processor 910. Apart of the memory 920 may further include a non-volatile random accessmemory. For example, the memory 920 may further store device typeinformation.

The bus system 930 may further include a power bus, a control bus, astatus signal bus, and the like in addition to a data bus. However, forclear description, various types of buses in the figure are marked asthe bus system 930.

In an implementation process, the steps of the foregoing method may becompleted by using an integrated logic circuit of hardware in theprocessor 910 or an instruction in a form of software. Steps of themethod disclosed with reference to the embodiments of the presentinvention may be directly performed and completed by a hardwareprocessor, or may be performed and completed by a combination ofhardware and software modules in the processor. The software module maybe located in a mature storage medium in the art, such as a randomaccess memory, a flash memory, a read-only memory, a programmableread-only memory, an electrically-erasable programmable memory, or aregister. The storage medium is located in the memory 920, and theprocessor 910 reads information in the memory 920 and completes thesteps of the foregoing method in combination with hardware of theprocessor 910. To avoid repetition, details are not described hereinagain.

Optionally, in an embodiment, that the processor 910 detects, on a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource, a first pilot sequence sent by a terminal deviceincludes:

detecting the first pilot sequence in a part of a subband of the firstOFDM symbol of the grant free transmission resource.

Optionally, in an embodiment, an element of the first pilot sequence isa non-zero element.

Optionally, in an embodiment, the first pilot sequence includes a firstpilot sub-sequence and a second pilot sub-sequence. Each element of thefirst pilot sub-sequence is a zero element, and an element of the secondpilot sub-sequence is a non-zero element.

Optionally, in an embodiment, that the processor 910 detects, on a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource, a first pilot sequence sent by a terminal deviceincludes:

detecting the first pilot sequence in a first subband of the first OFDMsymbol of the grant free transmission resource, where the first subbandincludes M resource elements REs, a non-zero symbol formed after thenon-zero element is mapped is an M-order Walsh code, and M is a positiveinteger and is an exponential power of 2.

Optionally, in an embodiment, the REs included in the first subband areM consecutive REs.

Optionally, in an embodiment, the first pilot sequence is in one-to-onecorrespondence with the second pilot sequence.

Optionally, in an embodiment, the second pilot sequence is asub-sequence combination including multiple sub-sequences.

Optionally, in an embodiment, at least two of the multiple sub-sequencesincluded in the second pilot sequence are sub-sequences mapped to a samesecond OFDM symbol of the grant free transmission resource.

Optionally, in an embodiment, all the multiple sub-sequences included inthe second pilot sequence are sub-sequences mapped to a same second OFDMsymbol of the grant free transmission resource.

Optionally, in an embodiment, at least two of the multiple sub-sequencesincluded in the second pilot sequence are sub-sequences separatelymapped to different subbands of a same second OFDM symbol of the grantfree transmission resource.

Optionally, in an embodiment, all the multiple sub-sequences included inthe second pilot sequence are sub-sequences separately mapped todifferent second OFDM symbols of the grant free transmission resource.

Optionally, in an embodiment, all the multiple sub-sequences included inthe second pilot sequence are sub-sequences separately mapped to entirefrequency bands of the different second OFDM symbols of the grant freetransmission resource. The second OFDM symbols are different from thefirst OFDM symbol.

Optionally, in an embodiment, the second pilot sequence is representedby using multiple cyclic shift values. The multiple cyclic shift valuesare in one-to-one correspondence with the multiple sub-sequences.

Optionally, in an embodiment, the grant free transmission resource is atransmission resource combining time and frequency, or a transmissionresource combining time, frequency, and code domains.

Optionally, in an embodiment, the apparatus is applied todevice-to-device D2D communication, machine to machine M2Mcommunication, or machine type communication.

Optionally, in an embodiment, the network device is a base station, andthe terminal device is user equipment.

Therefore, in an embodiment, that the processor 910 detects, on a firstorthogonal frequency division multiplexing OFDM symbol of a grant freetransmission resource, a first pilot sequence sent by a terminal deviceincludes: detecting, on different first OFDM symbols of the grant freetransmission resource, the first pilot sequence repeatedly mapped by theterminal device; and/or detecting, in different subbands of the firstOFDM symbol of the grant free transmission resource, the first pilotsequence repeatedly mapped by the terminal device.

Optionally, in an embodiment, that the processor 910 detects, on asecond OFDM symbol of the grant free transmission resource, a secondpilot sequence that is sent by the terminal device and that correspondsto the first pilot sequence includes: detecting, on different secondOFDM symbols of the grant free transmission resource, the second pilotsequence repeatedly mapped by the terminal device; and/or detecting, indifferent subbands of the second OFDM symbol of the grant freetransmission resource, the second pilot sequence repeatedly mapped bythe terminal device.

It should be understood that the pilot sequence transmission apparatus900 in this embodiment of the present invention may correspond to theterminal device and the apparatus 600 in the embodiments of the presentinvention, and may correspond to an execution body of the method in theembodiments of the present invention. In addition, the foregoing andother operations and/or functions of the modules in the apparatus 900are used to implement corresponding procedures of the method in FIG. 6.For brevity, details are not described herein again.

Therefore, in the pilot sequence transmission apparatus in thisembodiment of the present invention, a network device detects, on afirst OFDM symbol of a grant free transmission resource, a first pilotsequence sent by a terminal device, to determine, according to the firstpilot sequence, whether the terminal device is in an active state;detects, on a second OFDM symbol of the grant free transmissionresource, only a second pilot sequence corresponding to the detectedfirst pilot sequence, that is, detects only the second pilot sequence ofthe terminal device that is in an active state; and demodulates uplinkdata according to the second pilot sequence. Therefore, the networkdevice does not need to detect all possible second pilot sequences, sothat a quantity of detected pilots can be significantly reduced, andpilot detection complexity is reduced.

In another aspect, in the pilot sequence transmission apparatus in thisembodiment of the present invention, the second pilot sequence is set toa sub-sequence combination including multiple sub-sequences. For a samequantity of second OFDM symbols, a quantity of second pilot sequencessupported by the second OFDM symbols can be significantly increased.Therefore, a pilot collision probability can be significantly reduced,correctness of uplink data demodulation is increased, and a case inwhich excessive second OFDM symbols are occupied can be avoided, so thatpilot overheads can be significantly reduced, and more time-frequencyresources can be used for data transmission, that is, a datatransmission amount of a system can be significantly increased.

It should be understood that the sending module or the sending unit orthe transmitter in the foregoing embodiments of the present inventionmay perform sending over an air interface, or may not perform sendingover an air interface but performs sending to another device, so thatthe another device performs sending over an air interface. Similarly,the receiving module or the receiving unit or the receiver in theforegoing embodiments may perform receiving over an air interface, ormay not perform receiving over an air interface but another deviceperforms receiving over an air interface.

It may be understood that, for the brevity and clarity of theapplication document, technical features and description of anembodiment above may be applicable to other embodiments. For example,technical features of a method embodiment may be applicable to anapparatus embodiment or another method embodiment, and are not describedone by one in detail in the other embodiments.

In addition, the terms “system” and “network” may be usedinterchangeably in this specification. The term “and/or” in thisspecification describes only an association relationship for describingassociated objects and represents that three relationships may exist.For example, A and/or B may represent the following three cases: Only Aexists, both A and B exist, and only B exists. In addition, thecharacter “I” in this specification generally indicates an “or”relationship between the associated objects.

It should be understood that, in the embodiments of the presentinvention, “B corresponding to A” indicates that B is associated with A,and B may be determined according to A. However, it should further beunderstood that determining B according to A does not mean that B isdetermined according to A only; that is, B may also be determinedaccording to A and/or other information.

A person of ordinary skill in the art may be aware that, the units andsteps in the examples described with reference to the embodimentsdisclosed herein may be implemented by electronic hardware, computersoftware, or a combination thereof. To clearly describe theinterchangeability between the hardware and the software, the foregoinghas generally described compositions and steps of each example accordingto functions. Whether the functions are performed by hardware orsoftware depends on particular applications and design constraintconditions of the technical solutions. A person skilled in the art mayuse different methods to implement the described functions for eachparticular application, but it should not be considered that theimplementation goes beyond the scope of the present invention.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, reference may bemade to a corresponding process in the foregoing method embodiments, anddetails are not described herein.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented through some interfaces, indirect couplings or communicationconnections between the apparatuses or units, or electrical connections,mechanical connections, or connections in other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. A part or all of the units may be selected according toactual needs to achieve the objectives of the solutions of theembodiments of the present invention.

In addition, functional units in the embodiments of the presentinvention may be integrated into one processing unit, or each of theunits may exist alone physically, or two or more units are integratedinto one unit. The integrated unit may be implemented in a form ofhardware, or may be implemented in a form of a software functional unit.

When the integrated unit is implemented in the form of a softwarefunctional unit and sold or used as an independent product, theintegrated unit may be stored in a computer-readable storage medium.Based on such an understanding, the technical solutions of the presentinvention essentially, or the part contributing to the prior art, or allor a part of the technical solutions may be implemented in the form of asoftware product. The software product is stored in a storage medium andincludes several instructions for instructing a computer device (whichmay be a personal computer, a server, or a network device) to performall or a part of the steps of the methods described in the embodimentsof the present invention. The foregoing storage medium includes: anymedium that can store program code, such as a USB flash drive, aremovable hard disk, a read-only memory (ROM), a random access memory(RAM), a magnetic disk, or an optical disc.

The foregoing descriptions are merely specific embodiments of thepresent invention, but are not intended to limit the protection scope ofthe present invention. Any modification or replacement readily figuredout by a person skilled in the art within the technical scope disclosedin the present invention shall fall within the protection scope of thepresent invention. Therefore, the protection scope of the presentinvention shall be subject to the protection scope of the claims.

What is claimed is:
 1. A pilot sequence transmission method, comprising:determining a first pilot sequence to indicate whether a terminal deviceis in an active state; determining a second pilot sequence for uplinkdata demodulation; mapping the first pilot sequence to a firstorthogonal frequency division multiplexing (OFDM) symbol of a grant freetransmission resource; mapping the second pilot sequence to a secondOFDM symbol of the grant free transmission resource; and sending thefirst pilot sequence and the second pilot sequence based on the firstOFDM symbol and the second OFDM symbol.
 2. The method according to claim1, wherein the method further comprises: determining a first pilotnumber wherein the first pilot sequence is determined according to thefirst pilot number, and wherein the second pilot sequence is determinedaccording to the first pilot number.
 3. The method according to claim 2,wherein the first pilot number is determined according to an identifierof the terminal device, or an identifier of the grant free transmissionresource and an identifier of the terminal device, or a random numbergenerator.
 4. The method according to claim 1, wherein the first pilotsequence is mapped to a part of a subband of the first OFDM symbol ofthe grant free transmission resource.
 5. The method according to claim4, wherein the first pilot sequence includes a non-zero element.
 6. Themethod according to claim 4, wherein the first pilot sequence comprisesa first pilot sub-sequence and a second pilot sub-sequence, each elementof the first pilot sub-sequence is a zero element, and the second pilotsub-sequence includes a non-zero element.
 7. The method according toclaim 5, wherein the non-zero element of the first pilot sequence ismapped to a first subband of the first OFDM symbol of the grant freetransmission resource, wherein the first subband comprises M resourceelements (REs), and a non-zero symbol as an M-order Walsh code, andwherein M is a positive integer and is an exponential power of
 2. 8. Themethod according to claim 7, wherein the REs include M consecutive REs.9. The method according to claim 1, further comprising: repeatedlymapping the first pilot sequence to different OFDM symbols of the grantfree transmission resource or different subbands of the first OFDMsymbol of the grant free transmission resource.
 10. The method accordingto claim 1, wherein the first pilot sequence is in one-to-onecorrespondence with the second pilot sequence.
 11. A pilot sequencetransmission apparatus, comprising: a processor, wherein the processoris configured to execute instructions, wherein the instructions causethe processor to: determine a first pilot sequence to indicate whether aterminal device is in an active state; determine a second pilot sequencefor uplink data demodulation; map the first pilot sequence to a firstorthogonal frequency division multiplexing (OFDM) symbol of a grant freetransmission resource; and map the second pilot sequence to a secondOFDM symbol of the grant free transmission resource.
 12. The apparatusaccording to claim 11, wherein the processor is coupled to atransmitter, and wherein the transmitter is configured to: send thefirst pilot sequence and the second pilot sequence based on the firstOFDM symbol and the second OFDM symbol.
 13. The apparatus according toclaim 11, wherein the instructions are stored in a memory coupled to theprocessor.
 14. The apparatus according to claim 11, wherein theprocessor is further configured to: determine a first pilot number,wherein the first pilot sequence and the second pilot sequence aredetermined according to the first pilot number.
 15. The apparatusaccording to claim 14, wherein the processor is further configured to:determine the first pilot number according to an identifier of theterminal device, or an identifier of the grant free transmissionresource and an identifier of the terminal device, or a random numbergenerator.
 16. The apparatus according to claim 11, wherein the firstpilot sequence is mapped to a part of a subband of the first OFDM symbolof the grant free transmission resource.
 17. The apparatus according toclaim 16, wherein the first pilot sequence includes a non-zero element.18. The apparatus according to claim 16, wherein the first pilotsequence comprises a first pilot sub-sequence and a second pilotsub-sequence, each element of the first pilot sub-sequence is a zeroelement, and the second pilot sub-sequence includes a non-zero element.19. The apparatus according to claim 16, wherein t the non-zero elementof the first pilot sequence is mapped to a first subband of the firstOFDM symbol of the grant free transmission resource, wherein the firstsubband comprises M resource elements (REs), and a non-zero symbol as anM-order Walsh code, and wherein M is a positive integer and is anexponential power of
 2. 20. The apparatus according to claim 19, whereinthe REs include M consecutive REs.
 21. The apparatus according to claim11, wherein the processor is further configured to: repeatedly map thefirst pilot sequence to different OFDM symbols of the grant freetransmission resource or different subbands of the first OFDM symbol ofthe grant free transmission resource.
 22. The apparatus according toclaim 11, wherein the first pilot sequence is in one-to-onecorrespondence with the second pilot sequence.